I can see alot of problems in mounting it off the cam. Firstly you'll need a custom cam with a dirive on it, then that will put lots of extra load on the bearings and also a torsional load on the cam as it spins up and down that it's not designed to take. it will also put alot more stress on the cam chain at it will need to transmit somthing like 30 bhp to the charger.
Best place to mount it would be in the same location as the AC pump on the astra/vectra below the alternator. You can then run the inlet piping along the front of the engine and mount the oil cooler and IC/CC in the pod like the VXT.
The TB can be pre or post depending on the setup, there's a guide on the rotrex website.
