I'm about to get my Rollei 35 back in hand after a good CLA and some repairs. There's only one problem...30.5mm filters. Finding them is easy...finding them in-stock and finding exactly what I want is not. So, question: do I step up, and if so, to what size? Do I go to 39mm - much easier to find - and if so, is that going to get too large on the front of the Rollei lens? Opinions wanted.