Correct spine arrow for 56# @ 29" Predator bow

[Matt D.]

Set up: Predator Recurve 56# @ 29" (I draw 29"), elevated rest (Bear weather rest), 250 gr broadhead

I'd like to try the small diameter Easton/Beeman arrows. Playing around with the Dynamic Spine Calculator, and assuming an arrow length of 30" and 0" center cut (just a guess, may be -1/16" or so) the calculator says I need a 300 arrow. From reading others set ups, I would have guessed a 340 and a little longer than 30". I would appreciate any input from others shooting similar setups.