On a related topic, is there any reason not to use AN7H drilled bolts (in the head) in order to lockwire the engine mounts versus adding the unique lock tab washers that are more difficult to obtain?   I can't see any reason not to use the drilled bolts beyond the $4 cost from Spruce.   On other aircraft, I note we use a lock tab washer that fits into the hole on the isolator and those are an MS standard.  But Lancair specs an additional washer between the isolator and bolt head hence the hybrid lock tab washer requirement.    An AN7H bolt would seem to be a simple answer to avoid the lock tab washer.   I'm betting someone has already been down this road?