Usually once set is there, it's pretty much there. The wood cells in the belly have already collapsed from compression stress. Heat treating the belly into reflex may help a little, but it helps more if you do it earlier in the process. How much set does it have? Set is inevitable in wooden bows-that's why many people reflex the stave a couple inches before tillering so that after it takes its set, it will still be straight. Some causes of excessive set are high moisture content (especially in hickory and other white woods), uneven tillering, stressing the bow too much during tillering (going too fast, pulling the bow too much with uneven tiller, pulling it past the intended draw weight, etc) or improper design. 59" is pretty short for a hickory bow with a 28" draw, but at that width, you shouldn't get more than a couple inches of set unless the wood is too wet or it was stressed too much. Hickory is really hard to get dried out, it soaks up moisture like a sponge in high humidity.