Let Skully customise your leather saddle: Brooks, Wrights etc - trimming, tying, name embossing and de-hammocking.

Stanley: yes. Change the blade so it's razor-sharp. Score your line lightly first. Keep the angle that you score at the same each time. After two or three scoring strokes you should be able to cut. Use tape to mask/template what you're cutting off.

Not sure what to say about it being twisted... they often are, a little. I guess wear/stretch sometimes makes this worse.

I don't think the stuffing will make much difference, at a guess. But yeah I suppose if you're going to stuff it anyway, do that first.