When engine maker UL Power decided to retrofit an RV-4 with one of their engines, they faced an interesting problem, brought about by the fact that it was much lighter than the original (to the airframe) Lycoming. This meant that it needed to be mounted farther forward to keep the eight and balance correct, and this – in turn – provided a clever solution to mounting the engine for the power-plant did not sport the typical Dynafocal 1 mounting gear geometry.
The solution is an adapter mount that picks up the standard Dynafocal mount that was already on the airframe (and supports not only the engine, but the nose wheel strut as well), adds the necessary distance to make the CG work out OK, and then bolts to the engine mount pattern on the UL Power engine. The beauty of this is that you can adapt the engine to the standard engine mount on just about any aircraft simply by building a new adapter, rather then re-engineering the entire mount. A bonus is easier maintenance because of the increased distance between engine and firewall.
Not the first time this has been done of course – turbine conversions come to mind – but something for builders to think about if they are planning on using a lighter, more compact engine than their airframe was designed for.