Assuming the barrels are in sound condition I don't really think pressure is going to be your main concern. Some of the 1 oz loads in order to ensure they will reliably "Kick" any autoloader action they may be put in have a rather sharp recoil. This is not necessarily good for 90+ year old wood & particularly in a side lock. Most of the 1 oz loads I see today are 3Ľ-1 & these seem to have a particularly sharp recoil. If you can get an honest 3-1 or better yet a 2 3/4-1 load you should be good.

Miller/TN
I Didn't Say Everything I Said, Yogi Berra