Hi Roverman
Ian is on holiday at the moment, so I'm sure he won't mind if I answer one or two of the questions for him.
The compressor has an electrically operated clutch between it and the drive pulley and there is a pull switch in the interior to enable it (its controlled by the sytem after that) , so no power loss issues.
There is also a mod available to fit a much neater rotary compressor see Ebay item No 170109171451 . this has the advantage that you don't need to redirect the engine steady bar to clear the compressor; and it's lighter!
There are other advantages associated with this system. The heater box is completely different to the standard item and has a much better blower motor - so even if you're not using the A/C you get much better ventilation. You potentially also get electric windows as there is a location in the revised centre console for the switches - you'll need a set of the NADA window frames to go with them, or use aftermarket electric window conversion motors. (I'm actually using NADA frames myself but I did the research for the aftermarket ones and was pleasantly surprised and impressed)
As for reliability, there's not a huge amount of experience available to me - they are extremely rare in this country. There is one known problem, which odly enough is on the heating side! Rather than having the heater matrix continuously fed as on the non A/C heater box, the A/C cars have a vacuum operated heater valve controlled by a capilliary into the car's interior so that you get a genuine thermostsic control of interior temperature. The capilliary is almost invariably broken and, so far, we have been unable to identify a replacement part, either like for like or modern alternative. People I've talked to seem not to mind, on the grounds that their cars are summer show cars. That's not good enough for me and I'm still investigating how to tackle this.
The other potential area looks to be the knob / valve on the left of the centre console which controls the temperature. This is really a vacuum distributor with seven or eight (haven't got one in front of me to count) seperately controlled outlets on the rear. As well as temperature it also controls all the flaps in the heater box and the compressor clutch. Vacuum actuators are pretty standard but I could imagine that valve being a problem if there was ever anything wrong with it. I'm not looking forward to trying to commission mine either!
Appearance inside the car is arguably better than the standard interior and very professional. That's why I chose the system over an aftermarket one.
I actually imported a complete "resting" car from the US to obtain a system in conjunction with Ian (he sourced the car and I did the shipping). This was because A/C donor cars are vanishingly rare in the UK and because it looked simpler to get a car ready installed. I wouldn't say now that the latter was justified, but the rarity is, and that has a knock on effect on price. Not a five minute job to install either!
If you really want A/C I personally don't think there is an alternative that doesn't spoil the look of the dash. There are quite a lot of Australian and New Zealand cars with factory fitted aftermarket type systems that look broadly similar to the Rpver / Delanaire system fitted to S1 2000TC's. I really don't like the appearance of either. The only solution I've seen that worked visually was a Hong Kong car that had had the A/C installed in the boot blowing up out of the rear parcel shelf. It wouldn't be a huge leap to install under carpet ducts to get cold air to the front as well. But you would spend a lot of time on this with a non functioning car and no guarantees as to the result!
Hope that helps
Chris