Looks like we're the short sighted leading the visually impaired then
From what little I've gathered so far, the standard Type IV impeller cooling makes it hard to get a decent drive up to the charger, as usually pulleys have to be attached to the front of the impeller. The problem with this is that by time you come that far out from the crank, there is a large amount of leverage across the impeller and crank end.
I have heard that to be safe, you should run an outrigger bearing to take the side load of the charger belt so coming from the crank you'd have: crank, impeller, supercharger belt pulley with some sort of extension for bearing, bearing. I assume by this point the charger belt must be near the gearlever

.
With the 911 cooling, I take it your fan pulley must be further back (nearer the crank), and I assume that you would then have the option of a) having separate charger and alternator belts or b) Having a serpentine belt around the two.
Having never had the cowling off of a Type IV I don't know, but looking at the pictures in the manual, I wondered if the impeller couldn't be adapted to have the charger pulley grafted onto the back of it, hard up against the crank, with the belt coming up through slots in the impeller housing: if this could be done, you could keep the low profile of the original cooling, and reduce the overhang of the charger load.
Just thoughts at the moment: if the project gets off the ground, I'll see if I can't get hold of a scrap Type IV to take down and look at the various options.
One things for sure, the MOT preparations have confirmed that the first stage will have to be getting the car very much better than it is now: brakes, electrics and bodywork. Having said that, obviously if the plan (and shopping list) is finalised whilst the car itself is being dealt with, it would be easier to crack straight on with the charging/injecting rather than developing the plan much later on (if that makes sense

). Still all hanging on this potential 911 project I've been offered, so everything's still up in the air at the moment.