My BPE IO 540X engine is due to get built and delivered in a couple of weeks, so I want to get ready so I can mount it soon after it arrives. Some recent chatter on Matronics about misaligned holes between the mount and the firewall. sure enough I had the same problem. The plans say to drill one of the two top holes and then use one of the bolts to hold/pin it while match drilling the other top mount. HOWEVER, when one side was drilled, the other hole on the firewall was too far outboard of the engine mount bushing, I tried severall lthings to 'spread 'the holes so that they could be match drilled. Finally, I crafted a 1"x2" piece of wood that was notched on one end to fit the engine mount weldment to keep it from slipping and the other end I cut on an angle, and then used a plastic mallet to wedge the wood 'spreader bar' between the to upper bushings. By using the tapered end I was able to get the other hole perfectly centered and thn proceeded to match drill it. The other 4 mounts were relatively close after the above, however the lower corner mount was NOT flush with the firewall land protruded aprox 3/8". Others on Matronics mentioned similar experience and said that it snugged up easily when tightened. This was my experience as well.
Here you can see the 'spreader bar' used to align the 'other top hole with the firewall pilot hole
