1. Is everything done by eye? By that I mean cutting and curving the shields.
Yes, all done by eye balling it.
1a. How easy is it to do? By that I mean fine tuning it. Does the projector need to be out of the headlight assembly or can it be done while installed (though outside of the car)?
That took me like a minute of back and forth adjusting. When actually making the finalized shields probably a lot more time consuming as I imagine tightening the bolts or whatever you use to hold the shield may adjust the light a bit.
2. Is there any way of getting a compromise between the stock and the curved shield to the point where you'd still have HID high beams?
Yeah, I believe there is. Theres a guy on HIDplanet forums thats doing the same E46 setup as me but in another car and will be making his bixenon capable. He believes the straight shields work the same as the curved on these projectors which will make it very possible.
3. For the lense, you said that you had to grind down a notch. Was it on the lense itself or on the projector brackets?
Projector brackets itself. I merely took a dremel to it. Didnt want to notch the lens itself like the factory ones are. Would rather change the holder than modify the lens in any way.
4. Is the light pattern even across? No fading to the sides etc?
As far as I know the beam is pretty wide. The pictures I have shown are taken from maybe 10 feet from the wall and the projectors are sitting on the upper rad support much closer than the factory head lights.
Needed to get some further away shots. At this point have to finalize the functionality of the lights before going any further though. Other than throwing the clear lens on the stock projector
Hope that answers some of your questions