Wow Marvin, these are some really great, but difficult questions. I know I don't have the answers, but here goes anyway. ;D
(1) If a callmaker buys the toneboard and makes their own reed to fit it, how do they know that the reed is cut tuned correctly?
I think this is one reason I like to buy tone boards from Al. First off, I have never made a tone board. I would like to, but just haven't worked up enough gumption to try it. So I buy them. Al's comes with reeds attached. Some of the others out there you have to make your own reed. I know that changing the thickness of the reed and the width and length will affect the sound. I guess I have just been too lazy to spend the time, with a notebook, sheet of mylar and scissors, to really determine what those changes will do. Guess your forcing me into trying it. ;D
(2) If a callmaker is not a predator hunter/caller, can they really know how how to tune an open reed howler or distress call?
My personal opinion is yes. First, there are so many different sounds out there for the maker to listen to and try to emulate. In some ways that is much better than to try an emulate a sound they may have heard. They have to rely on the memory if they were to do that, and the memory doesn't always provide an accurate playback. Secondly, and maybe more importantly, in my opinion, is there is no correct sound. By that I mean, if you listen to a group of, say 10, each giving their rendition of a dying jack, you will hear 10 different sounds. Do all these guys fail when hunting, because they are not exactly like a real dying jack? No, of course not. I just don't think the "exact" sound is necessary. Just so the sound is pretty realistic, doesn't break up a lot, I think it is going to work just fine.
(3) How much does the exhaust bore contribute to the overall sound of the call?
(5) What is the optimum size of the exhaust bore of a call in the 3" to 5" range?
I am going to combine questions 3 and 5, because I don't know how to answer one without the other. Again, here is an area I have not experimented with. I have done a lot of reading about this issue however. Some say a stepped bore is the way to go. Others say a belled bore is the way to go. There have been some who have set up elaborate tests to try to prove one way or the other which is better. In my opinion, I am going to go with a finished, belled bore. I, first, like the looks of it better, seems to show more attention to detail. I think if a stepped bore is the way to go, we would see that in instruments such as the clarinet, trumpet, trombone, etc. they all have smooth, belled bores.
As to the actual diameter of the bore itself, you can find calls that have a 1/4' diameter bore, a 1/2' bore a 5/8' and on and on. I think if the bore gets large enough, then it does start to affect the tonal qualities. Again back to the musical instrument. the clarinet is small bore compared to the bass saxophone. And the bores are very different. In predator calls, take an open reed tone board and put it on a call body with a 5/8" bore and put it on a cow horn. Is there a difference, you be there is. Now, for the standard maker, I do believe there is some correlation between the diameter of the bore and the deepness and volume of the sound. But for the most part, you have to go substantially different, like the standard call vs. the cow horn to make that much difference. Can the user tell the difference between a 1/4' and 3/4' bore? Yep, probably so. But can the coyote? Probably not. To test this, have someone blow one then the other, with out you knowing which is which, while you are stand 100 yards away. I don't believe you could tell the difference. Use the cow horn and yep, you probably could. I have not tested this, just my opinion.
(4) If the toneboard is a great toneboard will a sorry excuse for a body have a detrimental affect on the toneboard?
Well, first, go back and read my response to questions 3 and 5 above. That said, I am not sure what is meant by a sorry excuse for a body. If that means the quality of the turning, my answer is a most emphatic no. That only has to do with the pleasing look to the call. There are a lot of the old time calls that were just plain old straight turned calls. Nothing fancy about them, not even fancy woods or colors, or decorations, or .... Yet, these old calls worked great and still do. That is, if you wanted to take that valuable, irreplaceable call out and use it again. :o
If you are talking about the difference in material, yep, there is a difference. Put the same tone board on a soft porous wood and then put it on a piece of turned acrylic. You will notice a difference. But again, and I have not done this, listen to them from 100 yards away and see if you can really tell the difference. And then ask yourself it a coyote or bobcat or fox really cares.
To sum this up, in my opinion, I think most anyone who can operate a lathe, or operate a hand drill, knife, maybe a dremmel, can make an effective call. The quality of the purchased reeds is just so good today, that anyone can do it. I think what is selling the calls is the looks and the attention to detail. Those things show up when one looks at a call, and the word get around. Caller John spends a lot of time making a finely detailed call, people hear that and want to by one of Caller John's calls. Caller Fred's calls are not well finished, show unfinished insides, shows scratches and tool marks on the barrel, and that word gets out. People shy away from Caller Fred's calls. Will they both call the predator in? Yep, probably with out much difference noted between the effectiveness of one verse the other. It is the looks of the call, the attention to detail, the attention the maker pays to the customer, all these things are more important than the internals of the call itself.
Well, you asked for it, so there it is. Even though I didn't start off intending to write a book, it seems I sure did. I guess I am an opinionated old fart after all. ;D