I am relatively new in this hobby and currently building a YAK54 whose assembly manual isn't really clear.

What I need to know is what angle (if any) the engine should be mounted. The manual says engine mount holes are drilled with an offset, to offset the built-in thrust of the engine - but the kit did NOT come pre-drilled so I have to drill the holes myself.

So, how should I go about drilling the engine mount holes?

Any help would be appreciated.

If you are setting in the pilots seat, the engine should be angled to the right one or two degrees and angled down by the same amount.

If the engine mount were mounted in the center of the firewall, the crankshaft would be too far to the right and too low in the cowl.

Therefore the engine mount must be shifted to the left when setting in the pilots seat and up so the prop hub will be at the center of the cowl.

You will have to reverse engineer the plane. A guess would be in the order of 1/8" from center on the firewall.

Thanks, this is exactly what I wanted to know.
Also, as I surfed around for this, I found the following: http://www.rcaerobats.net/thrust_angles.htm
Hopefully, this would be useful for others in my situation.

that's a good link to save to get the angles exactly correct....