Originally Posted by crank_addict

Resurrection.
Perhaps this may assist.

Using a Campagnolo Triomphe short cage w/ 14 - 30t six speed, 52 - 40t chainrings. (Btw: 2018 and finding the 'original' Campy, under 40t for this BCD is getting pricey.) Pushing the limit but the cheap stamped steel backside cage plate looks like havoc awaiting to snag something. No 'b' adjustment on this unit.

Mounts much vertical and really should be used on a long horizontal axle dropout allowing more chain on a cog. Or consider the derailleur / dropout mount stop. There may be some different casted positioning for these two derailleurs.

Swapped the rear derailleur to a Victory short cage. Reset the 'b' adjustment, fiddly and tiny casting at the pivot mount. Doesn't allow much but worthy to inspect. This derailleur has a better backside cage plate. Shifting improved.

Lastly, both above have replaced plastic Crapagnolo jockey pulleys for no slop aluminum / sealed bearing type.