I'm also interested in this frankenstein setup on my gravel/road bike. Which parts and chainring size are you looking in to?

Honestly, was inspired by bike sauce video. Converting the 11 speed grx to use a 10-51T cassette , with a GRX 12 speed rear derailleur.
https://bike.shimano.com/en-EU/product/component/grx-12-speed/RD-RX822-SGS.html



Get a grx 600 shifters on ebay or something, use my existing crankset, and up the cassette to 10-51T and get the RD-RX822-SGS and off to the races.
It's like a $400-$500 upgrade if you can get good deal on parts.

From Temu,
https://share.temu.com/UW85epHXFfA

I tried it, pad was ok as long as you don't have wide sit bones. It's not very wide. Seemed dense.
I like the material of the fabric. stitching seemed to hold up so far.
Ran a little long on the leg and size was a little big so i'm trying out a smaller size.
No pockets.
----
https://share.temu.com/JnHv9b63HDA

Ran a little longer
Pad seems supple
Runs big so Im trying a smaller size then usual
Does have pockets
Seems very breathable
Shoulder Straps feel good

Let me know how the brakes work. I was forever considering converting my 29er to monstercross using a sensah or ltwoo groupset, but I am unsure if the brifters can pull enough oil to make the 4-piston XT 8120 calipers work properly.

Not sure about your exact setup but the brakes feel so good on mine. Having more issues with the shifting then the brakes. Brakes were pretty straight forward except I bought the wrong brake bleed kit so I had to get another one with the two syringe with 4mm adapters, ala Sram style bleed.

SRAM 12 speed drive trains use different size chains and therefore different chain rings and cassettes, from 11 speed and 12 speed shimano.

So you need to replace the chain ring/s to work 11 speed chain and cassette.

Was thinking something along these lines too. I was looking at the wolf tooth that claims to be compatible with a range of chains. Any aliexpress chainrings that known to be good or maybe I should just switch to a ali crankset all together.

I got my hands on a sensah/sentyeh HRD 1X11 Hydraulic set but it didn't come with the crankset. Just the rear derailleur and shifters and brakes. I'm trying to pick out a nice crankset. My friend is willing to part ways with his SRAM RIVAL DUB crankset but it being 12sp, I'm thinking it won't work and not sure what kind of chain to get to make it work. I guess I can always try changing the chainring on it right? What do you think? Anyone have any experience with this? Would it work as is with the right chain? Any suggestions welcome! Thank you!

Update:
Shimano Deore XT 11-42T Cassette
Sensah HRD GRII 1X11 SRX Pro Derailleur
KMC 11 Speed Chain
SRAM DUB-WIDE BB
SRAM DUB-WIDE 40T Chainring
1.85 Cassette spacer.

After taking it all apart and trying again,I swapped out to 11 speed chain and works better and no longer using the larger spacer. I think this is the final setup.
Had some issues with the sunshine 11-42t cassette but I took a good sunshine from another bike and realized the cassette was the culprit this whole time.
I switched to a deore xt cassette and the bike has come to life!!!!!

Hydraulic brakes are working great and shifting is sharp and quick.