It would help to see it. But yes, sounds like you need to take some width or side facet depending upon the ratio at the fades. Long string will tend to result in whip tiller, so going to a braced string won't help with stiff inner limbs. Again, hard to say without seeing it. If you laid out 3/8" and are down to it, that's about 1:3. You could go a smidge thinner but remember it will come to you all at once so take really small adjustments. 1/2" is already perty thin.
How wide is it?
Any deflex/reflex?