I believe the size of the halyard line for the Catalina 22 was 5/16 being a former small boat Catalina dealer. For some reason I thought the 3/8 was too big for the sheaves. With that said, my suggestion is try a 3/8 and if too big, step back down to a 5/16 line and it would be nice to get one end looped to add a shackle to vs. tying the line around the end of the shackle. Usually the site store sells halyards and they like to add a few feet vs. standard length which I find is very helpful if not thoughtful for their customers.
crazy dave condon