Thanks for your answer...

Currently I'm using 195/50R15 and it's the only possibility: here in Italy there are absurd laws about tyre size, you can only run what is reported on the veicle registration and there are no possibility to ask for modifications...

My current camber is this one (yellow circles), with little difference between right and left side, so the average is -0.5°
I've heard that is possible to arrive at -1.5°, but I know that driving straight could be not so comfortable as now and tyre wear will be also compromised...