OPTION not RECOMENDATION - But with the Michie the recommended strongly against reversal. Based on THAT specific marque and tyre.
Steve - I do not pretend to be a TYRE expert - but these guys actually visit Avon, Metzler, Bridgestone (EU), Michelin etc regularly.
They don't just do bike rubber, they do cars, trucks, and heavy machinery. I think they have a pretty good idea.
And trust matters. As you say - Think on that when at speed - I don't have to, because I trust their knowledge and not just "street lore".
I do NOT choose to ride in the rain if I don't have to. But my long sustained high-ish speed trips for a month or so meant that RAIN was probable somewhere and thus wet weather grip on maybe (certainly in Spain) greasy roads is a foregone conclusion of necessity. And in the UK - well you can guess. This matters far more to me than de-lamination by riding close to the tyres dry load/speed rating - which I will never achieve on an R3. I don't "trailer" - leastways never have done; it might be something the future brings though I doubt it. Would be cheaper to keep a spare bike in the UK. I should maybe add that I am VERY sparse on brake use (and any tyre stress therefrom resulting). I cannot actually remember the last time I changed pads except in a full rebuild. OK I can - was the missus car.
This is all making the best of a poor situation anyway. None of this would even matter if there was a decent Z rated tyre to R3 spec available.
I've used the tyre place exclusively for all my tyres (bike,car 4wd) since I've lived where I am now - some 20 years. Their advice has always been honest and often in contrary to their wallets gain. And yes I do check prices elsewhere. But for a tenner difference - why go elsewhere?
You are free to do as you see fit naturally - but I will always ask their opinions and if they make a STRONG recommendation - follow it.