A few years ago I used some aftermarket "top hats" with my Passat, they didn't have quite the slant that the original OEM ones had. The spring puts a sideways pressure on the top hat, the hole for the strut got worn into an oval, which caused looseness and clunking. When I replaced them with OEM ones that fit properly, it was obvious that they fit much better.
Short answer, you could probably get away with it, but it might cause accelerated wear of other components... (my best guess, anyway)