I fitted mine sucessfully, passed mot and my insurer's are absolutely fine, just go ott on the quality of bolt grades, sizes, metal.
My seats had to be raised as the audi seats sit a good 40mm lower that the original t6 seats so this gives the option to utilise 40x40 box but go for the thick sidewall stuff. 3.6mm+
The drivers side needs to be offset to the right to preserve the steering wheel alignment but the left side aligns to the original seat box perfectly but you need to account for the offset and how to fix that safely.
The passenger side was far simpler as you dont need to align with the center of the steering wheel.
If memory serves, VW T6 bolts the seats to the seatbox with just 4 m6 8.8 screws, i changed those for m10s grade 9. something so far in excess of the tested solution.