I havenít found any place on the net that has a lot of info about 8x12 mods, so I thought I would post mine here.
While doing the initial cleaning, and busting my knuckles getting the chuck off, I decided my first mod would be making studs to mount the chuck.
I made the studs by parting the heads of some 50mm hex head bolts, and then turning down the last 8mm, so that the bolts seated against the bottom of the holes (the holes are not tapped all the way to the bottom).
How is the check normally mounted on the 8x12? Your mod looks the same same as the how the chuck is mounted on the 7x12s. Just curious, because I have finally mastered the 7x12 three-finger-chuck-nut-change.
From the factory, the chuck is mounted using 8mm socket head cap screws that fit into counter sunk holes on the back of the spindle face. The only way to get them out is with a shortened Allen wrench, a real knuckle buster.
Unless there is quite a bit more clearance on the 8x12, I do not see how they would expect you to fish an allen wrench back there and get enough leverage. At first I thought the stud and nut of the 7x12 was a PITA, but that does sound worse.
After you get used to the stud and nut approach it really isnt that bad, but when they come from the factroy the nuts are pretty frozen on the stud and it takes quite a bit of pressure to get them off. I lost quite a bit of skin on that battle.
Sounds like you may have found a small cottage industry! LMS sells those kits for $2 and I am pretty sure that there are no more than $.50 worth of parts there. I ain't knocking them either... I bought a set for my 4 jaw chuck. I just did not feel like messing with it!
Granted you probably would not get rich, but you have a good solution for what I am sure is an annoying problem.