Modern Vespa

Now that I've switched up to larger tires I wonder what tire pressures to use?

You've got to try a bit, what feels good.
My manual states 1,8 bar = ~ 26psi front and 2 bar = ~29 psi rear, for the OEM tires.

Since I prefer a bit more pressure than recommended, to suit my style (it makes the tire warmer, thus grippier on cold mornings) I run now 2 bar front, and 2,2 bar rear = ~ 32 psi. It does feel a bit sharper too to ride, takes away a bit of the vagueness.

I'd say the manual recommendations are a good set point, and then start ball parking the ideal.

130/70-12 Michelin Pilot Sport Front, 140/70-12 Sava MC 29 rear.
Soo happy with them so far. Their grip is awesome. The Sava is quite soft, semi-racing orientated according the maker, and after 2300 kms, I'd say it's about on the half way of it's life. My OEM Sava Monsum were absolutely toasted after 4400 kms.

Thanks. Before I saw your reply and for no real reason I bumped up both front and rear 2psi, ending up at 28F/31R, pretty much the same as you (allowing for gauge inaccuracy, of course).