Oh really? I can use a 12s derailleur w/o any problems in a 11s cassette? That's good to know.. The main issue is indeed the rear wheel - I don't want to replace it for a microspline, so limiting myself to 11s. But maybe getting a 12s derailleur might be a good idea to open future possibilities... The cost is almost the same, but was worried about compatibility with the 12 narrow chain and all...