Engine thoughts

Quote from Barry Smith (Acro Advanced)

Airframe development can only ever follow engine availability

Barry uses a VW conversion for his (aerobatic) aircraft and obviously, it works well.

Watch the Redhawksduo and also the Italian Blue Voltige Team flying in their  Fournier RF 4 using a 1200cc VW conversion with 39 hp and doing stunning aerobatics. John Corby designed his 'Corby Starlet' around a VW engine. In a competition in Australia it placed in the 'top ten'. Also 'Sonex' (by John Monnett) still trust in VW conversions.

Why not develop the VW boxer engine? My nomination -  use of a (throttle body) injection with fuel pump and a deep oil sump, a heavy duty oil pump, a header tank, dual ignition....

Another thought was may be using the BMW R 1150 or 1200 engine. Geared by a Hirth gearbox. These motorcycle engines with around 100hp are mass-produced. They offer excellent quality. Fuel injection is standard, even air-cooled and reliable configured, with starter, generator etc. Weight of the engine including gearbox is approximately. 78 kg, so near to the VW type engines. Sparparts are available, distributed worldwide for reasonable prices.