Mats supplied the following simple schematic with his cavity, along with some additional instructions. Most of these instructions are also posted on the net in various places, and on Paul's web site. A complete set of the instructions that arrived with my particular cavity can be viewed in this file: complete instructions.pdf.
The 'grounded screen' in the title may be a bit confusing to those of us used to using tetrodes in the more conventional manner, with the cathode at chassis potential. Due to the design of this cavity, the screen is indeed at "ground" for RF; for DC, it can be more precisely described as being connected directly to the chassis, and at a potential of 350v with respect to the cathode. It is the cathode that hovers above the chassis at ~ -350v. This requires a bit more complexity in the design of the power supply.