That's a lot of bow for 3/4" of width. That's the max width, or the width at the arrow pass?
I'd let the set it takes from being draw progressively farther determine the max draw lenght. Were one to tiller it down a few pounds as the draw lenght approaches 28", I would expect it to do fine out to that draw lenght. With just 3/4" of working limb, you may get a little set at 28"
Very nice job.