Thanks ducatiz, good to know the sealer can flex.
I'm sure my tank is actually shrinking back down a little. I keep my bike in the dinning room next to the radiator which might help! Quite a dry atmosphere.
Anyway, tank off at the weekend and I'll measure it so I can track if it changes size.
I stumbled across his company in Japan make to very nice 'factory' looking alloy tanks for Ducati Monster and Superbike models ...
http://www.moto-works.jp/beater/index.html Expensive at £1,400+ but they look like a Ducati Course product.