My favorite shooter (I alternate this with a Horne Hunter recurve, and a Hoyt Vectrix, but dont tell anyone) is a
Boo back-Boo belly (Tonkin boo) with a hickori core. It is 68" ntn and 1 5/8" at the fadeouts. Straight taper to 1/2" tips.
42# @ 28", I shoot it at 29" i guess, (Right now with uncut Axis 300 spine carbons) it is very fast, cronographed, zero handshock. Boo really can make a sweet bow.
Have made several boo backed bows w/heavy wood belly, some are fast but none as sweet as the one with boo belly.
Anyway, i glued in 3" of reflex, thats the form. So it came out with 2 3/8", and still keeps 1 3/8 of reflex after being shot more than once a week for about 4 years. Probly + 25000 arrows
Id say you can safely put 3" of reflex if it is that long. 5" would be pushing it, 1" ultraconservative.
K