Kenko Extension tube + Canon lenses.
I noticed that Canon 18-55mm KIT lense doesn’t fit to my Kenko extension tube, because the flange is a little bit too long on KIT lense compared to Kenko tube fitting. This works for other “incompatible” lenses too.
So, I picked up a dremel and vóila, KIT lense now fits to Kenko extension tube like a glove. I extended the diameter of the inner opening on Extension tube so that EF-S KIT lense now fits to it. Afterwards I flushed all the dust etc. from the tube with compressed air. Scuba cylinders to good use, eh?
Here is a photo from that extension tube after modification: