Front derailleur width???

Referring to the space between inside and outside of the front derailleur cage. Is there a standard width? Seems like everytime I set up a bike I am squeezing the cage to keep the front derailleur from throwing the chain. Granted I am using 40 and 50 year old parts...and I think a lot of bell bottom jeans got caught up in front derailleur chainring interface. And perhaps with thinner modern chains the space between the cage can be tighter than with the old "10 speed" chains.