I was kinda skeptical of the clamps at first also,, but having used them on a couple cars now,, I wouldn`t worry about the clamps at all,,,not one bit... The clamps can be moved up and down the strut to figure out exactly how low ( or not ) you want to go ,, kinda like very low budget coil overs,, and you could always remove and weld a ring in, later if you want.
Like TheDatside mentioned i have seen the muffler clamp method hold just fine also ,, it just doesn`t have as clean a look..