Well, for anyone who’s interested:
RR’s turned up next day, thanks Merlin. First I did a coast down test on a shallow slope to flat on dry mud. Wow. I went 30% futher on the flat with RRs, tons less rolling resistance, no brbrbrbrbr on tarmac.
Out on the FoD trails first I rode loose fine stone, on which I had noticibly less cornering grip, but they washed out progressively. A bit less braking and traction purchase, though. On dry hardpacked loam the diffence was a lot smaller. On damp hardpack, even less, very close to the nevegals in all areas execept over roots , they span out easily on those. I even got through some slimey mud without grinding to a halt.
Maybe the next experiment is something just a little more knarly on the front to up the braking capability which was the only thing I really missed. The overiding (excuse the bad pun)impression was that my bike had had gulpped a double espresso, it just zipped out of the corners a lot more eager to please. Liked that. I think in terms of smiles per mile in dry conditions the RR are good news.
