If you don't mind me asking for details, are you going to put the NPT side of the compression fitting directly though the side of a pot...HLT. I am looking to do the same thing...hence the questions.
Thats what I did...I put a washer over the threaded end, then put the threads through from the inside and threaded my ball valve on the outside...hmm I had a rubber washer or silicon oring in there somewhere as well...Once it was cranked down in place, i attached the coil to the inside with the compression fittings.
One important note...when tightening the ball valve (clockwise), it is easy. Once you have it cranked down against the keggle wall, your wrench is too wide to slide in between the fat part of the ball valve and the keggle wall.....why does this matter? If you decide you need to remove the ball valve for whatever reason, and you try to unscrew it, the ball valve comes apart into separate pieces and it is extremely difficult to remove the inner piece because there isnt enough space for the wrench.
I had to sacrifice an old flat fixed-size crescent wrench that came with a table saw long ago. It wasnt big enough to fit over the ball valve piece so I grinded it on my grinding wheel...then the opening was too big. I ended up using it anyway, by jamming an extremely small allen wrench between one flat side of the ball valve and the ground-down inner side of the wrench. With the allen wrench jammed in there I was able to crank it until the valve loostened up.
Which reminds me...The other problem with this method is getting a wrench down inside your kettle or keggle to attach the compression fittings. The top one isnt so tough but the bottom one requires a lot of unrestrained cursing. If you use keggles and try to attach the compression fitting to the threaded piece before putting the coil inside, it is too big to fit through the keggle opening....
I hope my pain helps you in some way...
Best of luck!