Frank,
I've got the Dragon Evo Corsa 180/55 on the back of my '97 900SS, no problems with the swing arm......but it did chew it's way through the standard plastic hugger
Still, it was a good reason to buy a nice carbon one from Ducati Kaemna
They were the only people who could confirm their hugger wouldn't foul on a 180/55 tyre, they ask you to specify the rear size when ordered so they can dispatch the correct version. Very impressed all round!
Cheers.