ughh..I wish I could get some video footage. In terms of falling while attempting a cutback I'm thinking it happens because of several reasons.
1) I get too high up on the wave and don't cutback fast enough
2) Like you said, too far forward and rail bogs
3) Not reading the wave, everything happens so fast
For certain waves particularly reefs/points or jetties 3-4 ft. I have no problem bottom turning then top turning down the line. But at my home beach break I only managed to do that about 5 times total since I started surfing...pretty sad, so a majority of the time I count my sessions to be bad

. But I remember ever good session I have and write down the conditions, swell direction, tide, time, etc. hoping that one day I'll run into those conditions again. Most of the time I end up with quick angled drops which turn into close outs or waves get fat and flat which make rides last a split second. I started using a 5'8 x 18-3/4 x 2-1/4 round tail, paddle-wise I feel fine, I can catch waves. I'm a skinny guy, about 125 maybe a pound more with a wetsuit.
However, I have an easier time popping up on certain waves while other waves I can barely get to my feet. I've been having a streak of bad sessions surfing in dropping tide and I've been having trouble popping up. I try to shake off bad session streaks, they tend to happen often no matter what size board I use. I'm just trying to build some consistency.
Last week I managed to pump along the face, it felt like I was weaving up and down the wave. It probably looked extremely ugly and was most likely a fluke but it got me stoked. That was the deciding factor to stick with the 5'8. Probably not the wisest decision for board choice but I'm chasing that feeling every session. thanks reply OMS.
btw, if anyone surfs regularly in the California Bay Area and wants to alternate to get video footage, feel free to PM me. I have a camcorder and everything.