Sandro,
I pondered how to cut the lip off for a little while and came up with the idea of using a 4-1/4" hole saw. I didn't want to use a gas axe or grinder as those methods can put a lot of heat into the metal - too much and you will weaken the tower structure near the plate bolts. The stock strut mount uses two slotted holes to locate the upper bearing and amazingly enough said holes are aligned with big hole in the middle of the tower. Cut a piece of 1/4" or 3/8" thick x 1" wide flat stock that is a little longer than the slotted holes. Measure the center distance of the slotted holes, then lay out those two holes and a third hole that is centered between those two on the flat stock. Find two bolts that just fit the slotted holes and drill the outside holes on the flat stock to fit the bolts, then drill the center hole 7/32". When you mount the flat stock on the bottom side of the tower, put 3 or 4 flat washers between the plate and tower so as not to saw the flat stock and center the 7/32" guide hole in the tower. Get a 1/2" or 3/4" variable speed drill, some oil to lubricate the saw and drill slowly - VERY SLOWLY. The drill should have a grip handle to help keep it from twisting around and breaking your wrist, believe me, the drill will try to do that. Take your time, oil the saw liberally so as not to burn it up. A half round mill file will take the burr off and leave a smooth hole. If you have a deburring tool, run that around the hole after filing, it leaves a rounded edge that won't open up your fingertips or knuckles. If you use this method, measure the outside edge of the lip before you buy the holesaw, I think it is 4-1/4" but don't quote me. Make sure the holesaw is for cutting metal, the ones for wood, plastic, etc will burn up in a heartbeat. Another note, this procedure worked on my A1 ('79) Rabbit, so I invoke the 5th amendment regarding any other Vdub. Baddaboom.