Hi Nigel,
I had the 265/75 on my 710, and later the 255/85 on my 712. Both were good fit for the applications, though there is only limited type of tires in the 255/85.
Though ATL had published the BF Goodriches in their lit, the MoD Pinzes had XZL 8.25s ( from what I'd seen) and the 718s that came out of our GL also had 8.25s. One of my old 710/12 manuals had listed the 8.25s for the 710/12 for UK use, but imo the tires are way too tall for the Gassers.... and the diesels for that matter too.
My preference are the 255/85 over the 285/75 for the most part, same diameter, and the 255s can easily air down to the 285 footprint without as much fear of debeading ( on the same size rim). The narrower tire mean less road resistence, and easier slow speed steering for the 710/12.
I might do some scounging for a set of 235s to see how the 716 likes them "on road".... I know the people I off road with won't... they're already peeved when I idle up or down a hill

... the shorter tires would only make it worse.

.
The Trojan Horse... the 1st Pinz used to covertly carry troops into battle .
ATL Pinzgauer XM 718K TUM(HD) 6x6 FFR (aka The Green Grail)