I'm not going to go intensely detailed about this, let's save that until I start trying uberman again.
The timing off my first core sleep is a bit off, I slept 9:00-13:30, and the only time I have to nap is 19-21. Therefore my core sleep should've been 5.45-10.15 to be exact on the opposite side of my nap. I hope that doesn't cause problems. I awoke pretty much on my REM sleep, so I'm not feeling completely destroyed, but I was still somewhat tired and took a gamble by lying in the bed awake for a while.
I don't feel much worse right now compared to say, sleeping 7-8 hours. I've gotten used to a least 9 hours, so even that made me a bit tired.