Yes. I've put the FPR ultra flex is couple of pens. Haven't fould the right pen yet. I have the Osprey Madison and bought 4 additional nib units with it. Feels like more than 1 pen but less than 2.
Best swap experience is with my Lamy nibs. I have a Logo and Aion. And several nibs, ef, f, 1.5 stub, and a 14k fine than I had ground to an italic. Everything writes great in either pen.