Wow, I didn't think I'd get this sort of response!
In answer to your questions:
Rad: Yes, I can regulate drips really well. Sometimes you only need to turn the bolt a touch but its really easy. The only slight issue is when I close the valve off completley, I still get a drip approx every 30-60 seconds. This was not an issue for me.
Kiwi: I thought about a ball valve but I think it would be much harder to adjust accuratley. I use one to regulate my coolant flow and it is not great. I think they are only really designed to be on or off.
LWTCS: I initially thought of using a nut on the top but I tried without first and I don't think it is required. I just screwed the 5mm bolt into the 6mm tube and it cut its own thread that seems really strong. I doubt you could strip it in normal use.
I will try and describe how I made it step by step.
My 5mm bolt is 40mm long
-Straighten and cut 2 pieces of 6mm copper tube, one a little shorter that the thread on the bolt and one as long as you want to go to your still.
-Take the bolt and screw it all the way into the short piece of tube. I used an impact driver for this as it was pretty stiff but you could use a spanner/pliers. Then remove it.
-Take the longer piece of tube and cut 4 slots in the end using side cutters going about 5mm down.
-Cutting the slots should create 4 tabs on the end on the tube. You need to bend two(opposites) of these out to 90 degrees. see below:
-Now take the piece of tube that you threaded and drill a 5mm hole about 10mm from the end:
-Clean everything and then put the two pieces of tube together, lining up the splayed end over the hole in the other piece. The difficult bit is getting them to stay on place so you can solder them. I got some copper wire(stripped down domestic electrical cable) and wrapped it round. You don't want ti to touch where you are going to solder though. The following pic is pretty rubbish but the best I could do:
-Solder up, making sure there are no gaps obviously.
-You will then need to run a 5mm drill bit down the tube(not the threaded one) to clean out any solder that got in and create a path through.
-Screw the bolt back in and test in water by blowing through. A tiny amount of air leakage seems ok.
You could use any size of tube/bolt I suppose as long as the bolt is a tight fit.
The bolt and threaded tube/bolt cannot be much shorter than I used as the top needs to be above the height of alcohol in the still to prevent leakage.
I'm not good at making instructions but I hope that it is helpfull.
Please ask if there are any more questions
. Will hopefully be making me one of these if I can find the right bolt soon enough