I don't see the need for such a heavy gun for ounce and an eighth or ounce and a quarter, but it will certainly work well. And it is a fabulous gun. If it indeed has drop locks, I sure would appreciate pictures of the out of the gun. I'm sure others would also.
I shoot ounce and a quarter lead in my six pound gun without any problem when upland hunting, which is proofed for that amount.
In your Westley, you could (and I do) shoot ounce and an eighth bismith loads using ounce and a quarter recipes for lead. Volumetrically, it works almost perfectly and gives lower pressure, a little more velocity, and excellent performance. Check out ounce and a quarter loads for Longshot powder in Winchester aa hulls and wads.