The 275/40 is too big for a Transporter and only used because it’s cheap! (it’s an ex Range Rover size so plenty of availability) we never have used this size in 20 years of working with Transporters like most others in the know - it seems to be mainly the online retailers who sell wheel deals who use the 275/40! . It’s between 5.5- 8.3% bigger than the factory sized tyres (16&17”), lowering with a 275/40 on the front at any decent drop will rub! The only place for oversize is with a 17” wheel when lifting a van.
After speaking with Supermetal wheels the other day, they have already got TUV approval on certain certificates for 265/40. The 265 is less than 5% oversize than all the factory wheels so perfect.
For 4motion you can use 265/40 both front and back and lower with no issues and with a staggered setup as we’ve proved and you retain your VW warranty.
On a 2wd you can also run the 245/45 on the front, and then even with a slimmer front wheel than 9”, with a staggered rear and 265/40. The difference is less than 1.5% front to back so unnoticeable.
Obviously my post is for T32 - There are other options for T28/30 as suggest above by
@Solow Suspension .
Pics so you can see they work as suggested
This is 9j all round 265/40 - Perfect
4Motion, 9j 265/40 all round
4motion van, staggered wheels with the 265 all round - perfect.