RE: Giant OMP Engine?
All engines have been used successfully but due to the altitude you will definately be at a dissatvantage. That's why OMP recommended the BME. Here's the ticket to try since you already have the engines: First go with the OS 160 with the Jerry Smith pipe accessory. If you are not satisfied with the performance then switch to the BME since it's already a beam mount configuration.
Mike
Team OMP