Selecting the rootstocks to use for stooling

First year bench grafting… I have about 40 rootstock of various types (bud9, bud10, m7, m111, g5) and am going to stool one of each.

Is there anything I should be looking for in that pile of rootstock to select one of each for propagation, or just grab any? I wasn’t sure if there were attributes that should be considered (larger root mass, larger wood, etc).

I do not think root mass matters so much. I try to get the hefty root ones on scions though.

I’m starting P.1, Kaido Crab, P.2 . M111 and G.214 as straight potted mother trees to grow out as trees to breed with. And will classic stool and mound stool the last 3 as my working stock. Will add P.14 next year with Dolgo Crab seedling.