They are probably using the different lengths so they can aim right on with the point of the arrow with different # bows.

 

Being over-spinned is not a big deal for compounds. For anything recurve it is a BIG deal. For indoor barebow I shoot some old Easton Fatboy arrows in 500 spine, almost full length with a 200gr screw in point. If I was starting over I would go with Easton Superdrive 23 in a 475 spine with some very heavy points. Even then they may be to stiff with your DL and DW.

You may be stuck with skinny arrows.

 

Thank you SHPoet. I'll give them a search.

 

It is a bit of an experiment getting to point on that close. Try some XX75 1716, those are the smallest aluminums that will take screw in points. They are only 29", but heavy for the spine. You could also get some Victory Vaps in 1000 spine, I think they come at 32 inch even at that rating.

I have a 29 inch draw and shot 34 inch arrows for indoor season. 350 spine black eagles with 200 grain points on 100 grain inserts from 40 lb bows.

 

It also depends on if you are shooting barebow, traditional, or longbow class. Barebow is allowed to stringwalk, so fast arrows will work. The other 2 classes are fighting a balance between a low enough anchor for alignment and an arrow that will give a repeatable sight picture. It doesn't necessarily need to be point on....point on the bottom of the blue or bottom of the paper can work.

 

I've been using 1716 full length (Bow is 31# on the fingers) even though my draw length is short. Longer arrows help bring the point-on down at 20 yards, but I still need to aim low to hit the gold. String-walking would, of course, bring it point-on but at the expense of bow balance.