Very nice work, the brass is spectacular. The Benson is already a small engine, scaling it down has to be quite a challenge.
I've just started a Benson Vertical a few weeks ago. However, I've scaled it up X1.6. I'll use aluminum castings from my backyard foundry. It's proving to be a really fun project. I think speeding up the governor is a good idea, I'll try to do the same. I'm in the process of casting the entablature now, I may move the governor mounting hole to make it easier to add a different gear ratio.
I'd be interested in how the piston rod bracket/bushing part of the project goes. It looks like it could be an alignment challenge.
When I get a bit further along I'll share a few pictures.
Bob