RE: lighter B/H for heavier Arrow
With 4 inch vanes @ 28 inches it puts you at 418 grains and 6.2 FOC with a 75 grain tip.
With 4 inch feathers @ 28 inches it puts you at 401 grains and 8.3 FOC with that 75 grain tip.
4 inch vains @ 28 inches with a 100 grain tip is 443 grains 8.5 FOC.
4 Inch feathers @ 28 inches and a 100 grain tip is 426 grains and 10.5 FOC.
Looks like you would be to light up front with those arrows if you went less than 100 grains up front.