I did have a scan in pdf format but is too big to attach and my IT skills mean I don't know how to get it into another format.
There are two options.
Vorti R, 265/35/ZR20 front and then 305/30/ZR20 rear
or the Vorti (harder compound):
stock sizes (255/40/20 and 285/35/20 which enables the front and rear axle tread patters to be used),
or you can go 285/35/20 square all the way round. But these will be the rear axle configeration which is not optimised for water disbursement (unlike the front axle tread pattern). Not sure how much of an impact this will have.
I know anil has bought some of these, I think the vorti R in 265/305 sizing and is getting them fitted in the next few weeks so should feedback then.
ATS did the exact same thing to me, the website claimed they were in stock, and weeks of chasing never got me anywhere other than timescales over 6 weeks. I was fortunate that I managed to get the rears from tyreleader but you've already tried themI've been having mega issues sourcing the MPSS 275/305 combination (the fronts are easy to get hold of, the rears not so much). Had a back order with ATS for nearly a month and today they told me they can no longer get the 305s direct from Michelin or any of their other suppliers. The MPSS 305 also aren't available from any of the online suppliers I've tried (Camskill, Tyreleader, Blackcircles, etc).