Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

It "looks" like Bruce fitted a rather fancy needle valve to get control...but we will wait for Bruce to tell us what Really happened 
  I had a question as well, did the boiler have a port for the pressure gauge, or did you "steal" a thread that was a mounting bolt for the Overtype unit Bruce?

You are exactly correct on both assumptions Ben , the pressure gauge replaced the hold down screw for the flywheel frame. I probably had 6-8 hrs in that custom valve , & not sure if I could build it today.
By far imho it's best regulated by controlling the heat source, a 200-300W immersion cartridge heater would do the job nicely.