Greg----I don't know what boolit you are using, but if the cartridge will chamber ok, it should work at that length. If you could supply a link to the boolit in question I might be able to make a better suggestion.
I would suggest you start at the lowest suggested powder charge listed or that you intend to use, and work your way up to where everything functions well and shoots accurately.
Burnt Fingers----- I ran a few magazines of H&G68 clones over 4.1 of WST through my 1911 and XDm over my chrono today. The averages were 774fps for the 1911 and 784fps for the XDm(5.25 inch barrel). If I remember correctly, 4.0 of Bullseye gave nearly identical speed and the same accuracy for me.