When I passed across @Happy Jack 's lovely Mike Lull P5 back to him, fitted with the new Andyjr1515 fretless neck, and watched him play it, I thought - no...we both thought - "that fretless neck ain't going to be swopped back for the original fretted one for a good while!"      For those who followed the thread, you will remember that the idea was that the two necks were designed to be able to be swopped over quickly and repeatedly with minimum fuss or reset.  Trouble is - and thi