Hi RobRover88,
It gave me advisory warnings in the info on the dash and I think went back down to normal off road height at a lower speed than normal off-road height returns to normal. I don’t recall the actual speed as I was on the gibb river road and a little hot by the time I got going again.
I have the D4 SDV6 HSE fully loaded including the factory diff locks. When I upgraded from the TD5 to the SDV6 I wasn’t up to speed with the 19” wheel and brakes issue. Once I started to set it up, for whatever reason (mainly $$) I didn’t go down the path of 18” compomotives with BFGs and picked up a set of 5 20” rims already fitted with 265 50 20 Nitto terra grapplers. They go ok but are no way near the BFG KA 02 I was running on the TD5 and with the lower profile don’t bag out too much when running reduced pressure off road.
Interestingly with the high day time and track surface temperatures versus the low in the evening / night I had to continually check pressures as they were then too soft first thing and then too hard after half hour or so. Unfortunately I staked it fair and square centre of the tread destroying the tyre.
Regarding the spare underneath, yes the 20” 265 fit and the winch works ok with them. Given trip preparations etc I always carry at least 2 spares for the car and had the second one in the off road camper so didn’t need to get underneath for the rear spare.
I still run stock front and rear bumpers for weight saving however do have upgraded underbody protection.