I have the front knuckles from 7075RC with the 22mm bearings and they are holding up really well. My rear knuckles should be here this week. That's a good thing cause I've blown 3 rear knuckle bearings lately. Also, the plastic rear knuckle bearing slots have stretched out and the bearings wobble around. I'm also running the Ramtech adapters to run HPI wheels. They are extended so they put extra load on the inner bearing. Upgraded bearings are a must. The reason I never swapped the knuckles, axles, and arms from my TT to my XB is that you don't get much more durability by moving to the 24mm bearings. Here's some radial load ratings on the bearings.
10x19x5 = 385 lbs
10x22x6 = 605 lbs
12x24x6 = 648 lbs
So you can see why 22mm's are the way to go. The reason the 22 and 24's are close in rating is because the ball size and races are almost identical. The 19mm balls are tiny in comparison.