I've got a slight butt tuck at rock bottom squats like I'm sure most of us do. My lower back muscles used to feel very tight after a high volume squat session, but I guess they got used to it after a while. I've 1rep maxed on squats and deads and have done 20 rep squats all without a belt and have not had the slightest pain in my back, not even stiffness. I remember reading somewhere that a little butt tuck is fine, you just need to build up slowly to let your lower back get accustomed to it.
I'm not going to say whether you should go as low as possible or not, but if you try, definitely allow some time to get used to it.
Oh well as long as the butt tuck thing is ok ill go lower. It just seemed like it made my lower back start rounding, but i guess its really not its just they way the body is? I didnt know if i could do my max weight that low.
Update, did maxes on weighted dips and deadlifts
dips
175x4
deadlifts
135x5
185x3
225x1
275x1
315x1
365x1
405x1
This was supposed to be my max, but felt like i could do more
455x1
Stoked about that
475x1
got this up! wtf i didntknow i could do this shit, hella happy.