Since about 8 out of 10 recurves are cut to center, including most of the older ones, it's a pretty good assumption in most cases. And a lot of cut to center recurves will shoot arrows spined right at their weight, and you're not drawing more than 28 inches, I see no need to go real heavy in spine. Might add 5# for a fast flite string, another 5# for a head over 125 grains. That puts you in the 60-65# range. Can go another 5# just for the hell of it. The bow will shoot them fine. Keep in mind, too, that with cedars, spines above 70# are becoming more difficult to find, particularly in 11/32 shafts. Be best to get a trial pack of several spines from one of the mail order vendors.