I pool all our boys into bachelor groups and since we're dual purpose I really watch their behavior, how they treat each other and how they're maturing in terms of their body structure and growth rate. The end goal being finding those future gentleman flock leaders of good quality for their breed, as well as having some amazing dinners. Seems to work out to be 33% are future leaders, 33% too mean/hormonal, 33% wonky in same way or too weak in social standing. It changes with smaller groups. So for every group that grows out (more than 10), roughly 66% are invited to dinner. I have a group of 14 boys running together now, so far at 3-4 months old there are 3-4 decent ones starting to show themselves. Here in 2 more months I can start making selections on who's sticking around for next year or who's getting matched up to extra pullets and moving on to be a flock leader elsewhere.
I've noticed our birds are getting bigger and the shape is really rounding out and getting wider, instead of the thinner/leaner/longer production layer type we've been culling out. I have a lighter weight layer type project bird I'm working on but have an outcross in mind that should flip it around to more dual purpose in type.
If you're the type to invite spares to dinner, I'd keep the nicest one who treat the others good, who isn't a total wimp and who has the widest distance between the legs. Just in case they make babies next year.