Ahh a bit of french bashing! The main reason why I don't post here regularly anymore.

If your going to replace the simplex deraileur on your all original px10 I believe you are missing out on the fun part of owning a vintage bike. Accept the good and bad points of your old bike and having to look after your parts. Dont' slam shift across all 5 gears at once, don't oven tighten the front mech. If the 40 year old part is past its best, find a better condition replacement.

The Simplex Prestige may not be in the top 10 best derailleurs of all time, but if its original to the bike then I'l use it. If Anquetil
could win the tour de france with them, then they are noble enough for me to use.