An extensive review of aircraft and engines was undertaken trying to find a plane that could do the job. It needed sufficient range and load carrying ability to make good distance and sufficient speed.
The real challenge is that aeroplane diesel engines are still in development. The team looked at Centurion, Dieselhawk, SMA and many others trying to get the right combination of weight and speed. The SMA diesel engine was the choice as it was a proven concept and importantly certified for the Cessna 182. Dieselhawk have a firewall forward package available for the RV7 but this is not ready yet and is awaiting certification but looks like a great combination. Other engines are also in development for the Cirrus. Progress on diesel engines will be boosted by Cessna having their own project on the go. At this stage, there is still a long way to go before all options are available.
Critically, the team also wanted a stable platform and one where the weight and balance numbers were well known given the loads that were going to be added with ferry tanks.
This led to the well known C182 and the certified SMA diesel 182 engine.