Same as your crow calls, just make every thing thinner, the channel and the reed to start with. Next shorter reed, a shorter thin reed over a thin tonechannel is what you are looking for.
Most I make are not made with the double boards, pain to keep the reed in place while shoving it down the bore. Look at the T20, and go with that route. Questions? Send me an email, I will find that quicker.
Marvin