Hypothetical question?  I have a 30 inch .500 deflection arrow with 200 grains up front.  It flys perfectly from my bow.  I want a heavier arrow.  With all the options we have today, I should be able to add 400, 500, 700, grains to the front of a .400 arrow and make it fly as perfectly as a .500.  Anybody know how much that would be???

And if that was a 28 inch arrow would the amount be the same?  Actually I'm sure it would not or it would be in Stu's Calculator.  LOL!!!  I would guess that since the shorter arrow is stiffer it would need more weight.

Bowmania

Roughly 100 grs of point weight going from .500 to .400.There is app 20 lbs of spine difference.To change dynamic spine 5#,bows I own go from 15-25 grs.It would depend on the bow but I would experiment with adding 100 grs first,with .400 deflection.

With my Beman MFX arrows I can bare shaft them to tune the same with a 500 at 28in and 225grs of tip weight and the 400 at 30in with the same tip weight off my 54 and 56# BW bows.  My 500 wieghs 520grs and the 400 weighs 560grs.

I think some careful data entries into Stu's DSC would get you into the ballpark, just choose "OTHER", run the deflections through his ASTM to old AMO converter, etc.