I've been looking at the LRC some more, and ordered an RF Hanger (LRC) from RDRP...
It turns out the thing has exactly the same geometry as the 0 degree anti-squat one from the DEX210 kit!
So the LRC kit from RDRP only makes a difference when you run anti-squat.
So for anyone looking to try a low roll center: Buy a 1.5 deg or 3 deg RR hanger seperately - you don't need the RF or 0 degree RR hanger.
I've been looking into why they didn't lower the RF block. It turns out the suspension arm would rub (quite seriously) on the chassis plate. Then the question remains if it may be preferable for the car's handling if the RF hanger is lowered any further - I'll be looking into that next.
EDIT: I have been looking into this: It turns out a TRF201 has a 3mm lower roll center at the RR hanger (both cars adjust the roll center at the RF hanger). That's quite a difference. I can't measure other modern 2WDs at the moment, but I think most cars won't be around the 210's roll center, but around the one of the 201.
EDIT 2:
I've put the roll center in a CAD model. Thanks to Jimmy's nice X6/B4 comparison pictures in one of his reviews, it's easy to compare the differences:
The DEX210 inner hinge pins and ball studs are about 3-4mm higher than the B4's. The X6's story is more complicated: On clay I recall the ground clearance should be the same as the way the B4 is pictured, so that'd put the hinge pins at a similar height (but further apart) and the gearbox higher up.