Chris,
This link
http://www.davegoodfellow.com/plans.pdf seems not to have any plans.

I did have a look on your web site,

so I can see the resemblance but it was my own design. (I have the drawings to prove it). There again all wobblers look pretty much the same.

I did this one to work on lung power, but it kept on making me dizzy.

The way it is in the photo it will run on 2 – 2.2 psi now invert it and it will run on 1.8 – 2 psi.
The two inputs allow it to run either way – to show I was not cheating.

It runs upside down better purely because of gravity. Gravity acting on the piston/rod.
(Something to remember – especially with tiny engines)

There is no gasket just two small bits of inserted copper pipe and
hope.It must leak slightly but never noticed it, also oil gets in there which probably helps with the sealing. Only running on 2psi.
Then there is the spring – perhaps the most important part of a small wobbler.
Another thing Chris I deliberately gave it a load of “bling” a lot of spit and polish, there is no reason you cannot “bling” your Brassy Babe up – makes it a whole new engine.
DaveH