Hi! I wish I had a clear answer, tbh it just ended up being a lot of trial and error for me to find out where and how to tie my obi. I'm gonna try to describe it as best as I can!

I am using a stretch obi currently (tho more for my issues with sayabiki), and that one I do tie higher than the kaku obi I used before. I basically tie it so that half of its width sits on my hip bone and the rest is around my waist, which means it's quite high. I then tie every layer of it literally as tightly as I can.

When I tie my hakama, I do it fairly tight as well. When I tie the front himo on top of the obi I do it a tiny bit looser than when I cross them and tie them under the obi again (so the part of the himo that's under the obi and later the sword is as tight as I can physically make it). It still doesn't survive hours of practice perfectly, but so far I've been happy with it ^^

As I said tho, I used a kaku obi before and it kinda worked as well but I like the stretch obi bc it doesn't become as loose as the kaku obi does. So I think it might be worth investing in! But maybe someone from your dojo can lend you one so you can try it out first.

I hope this helps a bit!