I guy brought me a bass he bought 30 years ago to get it back in playing condition. It has a P neck the previous owner made fretless, a DIY spalted body, Dimarzio P pickup, P bridge, etc. The frets were removed, and he must have had problems with chipping, so he routed about an 1/8" slot at each fret, and filled them with a slightly lighter shade wood than Rosewood. AND he removed the truss rod. The back of the neck has a 1/2" route the length of the neck, from the back of the neck to the back of the fingerboard, and it's filled with wood. I imagine the guy who did this was an upright player, and since an upright has no truss rod, why would a fretless bass need one. I planed off a "ski-jump" at the end of the board, and without strings it's flat, but with the rounds he has on them, the neck has too much relief. I need ideas. I suggested to him going with low tension strings to try and keep the neck reasonably flat to get the action where it should be, but I have little experience with low tension strings. Where do I go from here? I will post pics later when I get back to my home computer.