You are looking for perfectly straight grain if you want the bow to be unbacked.
If the grain isn't the best then back it with some rawhide first.
The best bet is to keep it straight to begin with and forget about adding any reflex.
Learning how to tiller full stop is the hard thing. Once you understand the process and that as wood gets thinner it can and should be bending more are the things that take a awhile to sink in. However once you understand then any bow is the same to tiller.
BH - why do you keep saying but what do I know? Everyone understands you can make a good molly. This chap could obviously learn a lot from your advise. False modesty n all that?