Don't have any experience with this plane, but regarding thrust, suggest you fly the plane a few times prior to installing or cutting the cowl. In my experience, this isn't a bad plan even if the firewall appears to be marked well. Doubt seriously any up thrust will be required though.

As far as locating the engine on the firewall, you can do a lot of messing around if this is done prior to installing the flying surfaces, by just setting the plane on the tail and scooting the engine/motor mount around while test fitting the cowl. If the engine's cylinder head is getting in your way during this process, often you can "rig" a piece of dowel in the motor mount, located to mimic the crank center line.
Best of luck on your builds! -Al