I likewise shoot a Katera XL at 29" DL. For optimal spine, use a .400 arrow and cut it at 29-29.5" and tip it w/ a 125gr. tip. If you're looking for SPEED, at 55#, you coul get into a SHORT 27.5 .450-.500 spine arrow and tip it w/ a 75-90gr tip (I'd have to run the numbers, but I know something in this range should/would work). At 68-72#, I ease of in the later season when it gets cold, I shoot a .340 spined arrow that is 29.5" long, and has a 125gr tip on it. These are actually a touch stiff for the lower weight setting, but still fly quite well even w/ a BH on the fore-end. Hope some of that helps.