Keep them long to start. I would do 30” if not full length. Hard to say for sure more than that without more info on your bow like type and center cut. Still lots of variables, but the 3555 should work for most bows at that weight and draw length if cut to or past center. Are you set on the 125 point? If you are, then you really want to start long. If not, then you can probably get away with the 29.5” and play with points and then cutting to fine tune. You would have 1.5” of cutting room. I have shot them, but with most of my bows around 50-55@ 29 and 30” minimum arrows, they are getting too light most times. I could do a lot more with them if I could cut them 1” shorter.