I think my biggest concern for writing the original post, was that if I mounted the engine upright on a low-wing aircraft, it woudl raise the Cof G significantly in the "z" direction, making it a little less stable in "roll". Presumeably the "pitch" CofG would be unaffected. Anyway, thanks everyone for taking your time to respond.
If you think about it upright, inverted or side mounted engines will not affect the roll provided the designed thrust line is not changed.
Ed S