Ken. It sounds like you know what you are doing. If you wont try to play a c then you will never know if it's right for you and the next time someone asks you will decline again or go the transposition route. Either way it doesn't seem right, does it? I don't own a c and have played one one time with marginal results but then again, that was the only time I had an opportunity to need one. Lots of trumpet players here on TM show a c in their signatures along with flugels and piccolos so at some point they were successful enough to need them. You owe it to yourself to borrow one and try the music out for your own piece of mind. Heck, if it sounds squirrely you still can fall back on the transposition to avoid embarrassing yourself. Keep in mind that time is the factor that may keep you from using it, so quick like a bunny and get practicing. Best wishes.