Many years ago, before the ready made engine mounts became available, the most common way of mounting engines were long hardwood beams reaching deep into the fuselage. I am aware the engines were smaller at the time, but at least the whole front half of the fuselage supported the engine.

In my opinion the rather thin ply plate on the 109 lacks some stiffness. This may lead to flexing of the plate, transmitting hard vibrations to the fuse. I am contemplating glueing two hardwood beams to the underside of the ply plate, each side of the crankcase opening, letting them reach all the way from the front plate to the firewall, and glue them securely at each end. Maybe 1/2" x 7/8" would be a suitable dimension. This should add considerable stiffness to the engine mounting plate.

It may also help to add a beam behind the engine, on top of the ply plate across the engine compartment.

Perhaps this is overkill, but the added weight will not be dramatic, and I think the stock arrangement is a bit weak anyway.

Helge.