Hill Wesley Special, Dacron string, 57@28 drawn to 28.5". I want to shoot 160 gr heads with an arrow 29.75" long, what spine you guys think it will take?
Probably 60 to 65#. Hill bows like spines on the light side, it seems to me.
Here are my figures: 58 lb draw + 10 for the longer shaft and + 5 for the 160 heads equals 73 lb. A Hill will generally shoot a little below weight with the regular depth of shelf cut, esp with a dacron string, so I estimate 65-69 lb spine. You have a little extra shaft length to tune with and should be able to get these spot on.
I'm right in-between. I'd go 5# for the extra shaft length and come up with 65-70#. In truth, all probably will work, but one will work better than the others. I recommend you start with a test kit with the three weights suggested so far.