Managed a full send on the Cloud's Rest FKT, on the variation from Happy Isles via the JMT!
Packed 1.5L of Tailwind in an Osprey hydration pack, and had 3 Spring energy gels enroute, and one just before the start. Pushed to the Nevada Falls bridge (and would've pushed harder if I had checked the Strava record for the section! I ended up being off from the crown by 2 seconds haha) as that section is very runnable, and you can charge on the flat sections early in the morning pre-tourist. I pushed through the flat sand in Little Yosemite Valley, and then started in on the grind up from there.
I think the ascent could be done in under 2 hours if one could push at the start, and still have enough gas in the tank to run the vast majority of the climb to Clouds Rest. The trail is moderate and very runnable, although steep and/or rocky in some sections that made me walk, but I could have pushed harder with better trained quads! The descent is a mix of mostly runnable trail with some technical sections, and lower down, just a LOT of tourist dodging. Maybe do the climb by headlamp so that you can descend while it is still too early for the tourons? Not sure, but either way wasn't sure how to shave much more time off of coming down.
Highly recommend this route, and especially doing it just for fun as well so you can spend some time on the summit with some of the best views in the park! I came up for sunrise while on a backpacking trip with some friends and we spend a couple hours up there.