if you want maybe 4-5 tops each, sure.
you gotta worry about rigidness of the stem, but in general you should wait until enough future virtical colas exist... i'm not a fan of lil axial buds with virtually no dvelopment.. i'd like to see a little branching at least start.. doesnt' ahve to be substantive, just more than a nub at a growth node.
8 plants in a 4x4? So, 4-5 tops might beright.. that'd be 32-40 tops.... so maybe a few more wouldn't hurt. how many colas you want to fit in there? work backward fro there. depends a lot on the plant you grow... if more of a lanky / non-branching type, you'll want more for sure. otherwise if it bushes out like crazy, it might be time to give those 4-5 branches apical dominance.
getting it even early makes it easier to keep it even late... when you do lst, don't be afraid to temporarily bend some more advanced growth down and give some smaller growth a lions share of resources for a bit.... sometimes just bending down the bigger ones in morning is enough to break apical dominance for the day. other times you may need to phyiscally tie something down for a few days. anyway, much easier to do this when they are all just a few growth nodes long... their vascular tissue will develop at a similar rate etc... all things that domino into benefits later.