Richard,
Yes we did, finally. There were multiple reasons it was not running properly, and was difficult to start. I will list them:

1. The fuel metering pop off pressure was far too low. I adjusted that up to 25 psi, within manufacturers specification. Causing rich mixture.
2. The fuel metering lever was set too high. Also causing rich mixture.
3. The carb was hard mounted and subject to engine vibration and possibly aerating the fuel interfering with pumping and metering.
4. The welch plug was by-passing. This, combined with 1&2 would have caused the engine to run (still rich) with both tuning needles fully closed.

I have now mounted the engine on a rubber mount, contrary to all the advice from my mentors. We tested it out in the plane at the weekend, and the early indications are that this is a totally successful method to reduce the vibration down to a flyable level. This has turned around the viability of this engine to power the plane; I now think I will go ahead with it.

Video here of the temporary trial installation. The carb is not properly mounted. I am installing it permanently today. : https://vimeo.com/181367442

The carb is the original chainsaw carb. I will have to design and make a more suitable one after the plane is registered and test flown. However, this works ok and is quiet enough, just a bit ugly.