Richard,
My mistake - both Hots should be disconnected from the load.
As for use of a 3 phase motor starter on single phase motors - I rechecked my facts (based on recommended wiring documentation for A/B motor starters) first leg should be routed through first two contacts as described and second leg through the third contact.
I missed the melting thermal overloads on the ebay auction - for that particular starter your method would be fine, but that starter's overloads are not resettable and I would avoid it. Most conventional starters use bi-metallic thermal overloads that should each see the same current - thus the series wiring of the hot leg through the first two contacts and second leg through the third contact.
Your point about controlling the coil on the motor starter with the pressure switch is also good.
Fuseable disconnect? If a circuit breaker / disconnect is within line sight of the compressor, a disconnect is not required. Not sure what value a fuseable disconnect would have if the CB feeding the line is sized appropriately for the wires you are using in your starter box.
One additional note on wiring to the starter - after razzing from Tony about a year ago . . . I fed my starter box with 4 wire single phase (H1, H2, N and G). I used H1 and N (120V) for the control ciruit (motor starter coil in series with the pressure switch) You should put a 1Amp slow blow fuse in this circuit right at the motor starter location to protect the control circuit wiring.
