Ok, so I've done some measuring. It must be said that the van was on our driveway which is block paving and not perfectly level so not an ideal surface for precise measurements. Having said that, I measured the same wheel (rear nearside) each time, so I believe the measurements relative to each other are fairly accurate even if the absolute numbers may not be directly comparable to other people's measurements!
This was done on an LWB T6 with VB air suspension on 235/55/17 tyres set at 48psi all round. The pop top is a Reimo Easyfit, i.e. definitely not a slimline one! All measurements in mm.
Firstly some general measurements to allow conversion to other measurements of interest, e.g. total van height, etc.
Ground to wheel centre: 325
Total wheel height: 665 (more than 2x measurement above due to tyre compression)
Top wheel arch to top of van: 1240 (add this number to the numbers below to get total van height, slightly rough due to curvature of van roof, etc)
And now the measurements from ground to top of wheel arch for each VB setting:
Car park crawler: 670 (Low speed crawler mode only)
Sport: 730
Normal: 750
Off-road: 785 (Low speed mode only)
I hope this is useful. I guess the numbers are reasonably comparable with the ones you quoted above. The main difference is that the car park crawler mode is rather lower - I really can't imagine the car park crawler mode on ours going much lower without serious rubbing issues! We can definitely get under 2m barriers in ours, and that's with a pretty chunky pop top.
The lowest driving height (sport) is almost certainly still a fair bit higher than your current driving height though, which I think is your main issue.