basically, on alot of the tw classic subs, the lugholes on the case are not centered, they're closer to the outer edge, so if one was to drill the holes to fit the 20mm springbars, there's a good chance that the hole would hit the outermost edge completely, which is just no good.
so, a few of us are trying to figure out to redrill these holes more towards the center, basically would have to start the new hole on the flat surface of the current, closer to the center of the lug. the problem is that the 1.3mm bits used to drill these holes arent the most sturdy of drill bits, so the odds of them breaking and damaging the case are likely, so we're trying to figure out how to remedy this problem, i.e. shorter bits, drill press, etc.
its a bit of a headache, but i think we can get it done :)