Six jours, I have no problems whatsoever with the 20T jump with the Huret Jubilee FD. It handles it with aplomb, and there are no chain-rub issues in either ring, either. And, having a very flat cage, it fits well with the narrow gap between the crank arm and the outer ring. My only gripe is one of cosmetics: the Jubilee cage is shaped for a 50T ring, so it's not perfectly concentric with a 46T ring. It gives the appearance of not being fit properly, but this is strictly a style point, and does not impact the functionality at all. Also, being that the Q factor for this TA double is only 136mm with my chosen BB, the FD cage comes within a couple of mm of the fender when positioned on the inside ring. Again, a non-issue but it could have been had the Q been any narrower or the fender any wider.

Here's a closeup:



By the way, I've seen your own bikes, and they are stunning reproductions of some of my favorite bikes of different eras. Top-notch, to say the least. I especially love your 1952 Herse Rando copy. Carefully thought out with all the right details. You've obviously done your homework on these classics.