Engine Mount Question

I'm trying to find the exact location for the engine mount in my Sinus, and it's causing me difficulty.

First off, I know that airplane engines are often canted a few degrees because of uneven thrust by the propeller. Maybe this is the entire root of the problem.

Anyway, the engine mount bolt holes are not equally high on the firewall when the mount is held in position with an approximately equal distance between the mount and both sides of the firewall. The top-starboard (top-right, looking toward the nose) bolt hole is perhaps 1.5 cm lower than the corresponding hole on the port (left) side. The two outside-bottom bolt holes are offset in the same direction, but about half as much. They still look mountable on the pads, but they're different.

This is with the bottom-middle bolt hole offset a little toward the starboard side, but still on the mounting pad there. I have it the recommended 42 cm above the outside of the fuselage, as best I can measure that distance, which is difficult. I see that in the factory manual, it shows this same situation--the bolt offset a bit to the starboard side. On Paul Kuntz's site, it shows this same bolt squarely in the middle. The top bar of the engine mount appears to slant slightly to starboard, though I haven't put a level on it. The fuselage itself is not exactly level as I have it supported.

Measuring between the top and bottom outside engine mount holes, it's a slightly different distance between them, by maybe half a cm, with the port side a bit longer.

As soon as I decide whether the bottom bolt should be more starboard, more port, or neither, then I'll drill that hole and more accurately locate the other holes. But I think I've done it accurately enough already to see the difference I described above.

Hmmmmm....I measured the 42 cm from the lip of the outside (bottom) of the fuselage. But the surface slants downward as it passes underneath the firewall. Is that where I should have measured from, and if so, how? This gets more complicated by the minute. I suppose those top fittings on the engine mount have to meet the cowling.

So...I wonder whether I should worry about this, or should I just drill the holes and be done with it? Is there anything I could, or should, do?

Questions, questions. If I didn't come up with so many things I need to stop and figure out, I'd have a lot more done by now!