That's crazy that you can fit 5 in such a small space. I was more concerned about width vs height but now you got me worried lol.
Use cable ties as the branches try to grow outwards, that'll train them to grow up rather than out, or if you're LSTing maybe stick it in a corner and have it tied down towards the middle of the tent, i don't know why but that angle seems to work best in my head, but I'm not using a rectangle tent like you, you'll find a way that works best for you anyway


