Tyre size is not so horrible, it's a big 33 inch tyre so even on a 20 inch wheel it's only .75 inch less sidewall than a 33 inch 17.

SNIP

Hmm, Check your maths Captain.

The Defender wheels are 32" ( 255 / 60 R 20)

So if two rims are both 32" diameter. One wheel has 17" diameter rims and the other has 20" diameter rims. Regardless of width.

The sidewall difference is the difference between overall diameter and wheel diameter divided by 2.

The 17" sidewall height is (32 - 17)/2 = 15/2 = 7.5" or 191mm

The 20" sidewall height is (32 - 20)/2 = 12/2 = 6" or 151 mm

That's a difference of 1.5" or 40mm in sidewall height by my calculations. So let your tyres down to say 16 - 18 PSI which will take about 60mm off the sidewall height. 17" is not perfect but the more the better. Especially since the tyres are only a soft spring when pressure is lowered.

The 17" setup now has 130mm of sidewall left

The 20" setup now has 90mm of sidewall left.

Get a ruler on a table and measure 90mm and imagine your rims that close to the ground, then measure 130mm

If you could go to 33" the differences are the same, but with 12mm more sidewall for both rim sizes.

Then there is the issue of even buying that 20" inch tyre that fits in anything other than a high speed highway tyre, something that needs cutting or suspension mods, or cheap unsafe Chinese ebay tyres.

If these issues could be resolved, especially tyre availability then it certainly makes the Derender more viable. But I repeat, 20" rims for an off road vehicle is just stupid UNLESS it can take large tyres. IMHO of course. Maybe it doesn't matter to many people who are the target market.