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I had thought that this causes lens decentering if a person replaces the front element, since you have lots of experience, are you saying its not a factor?
The 24-105 front element isn't a centering element (although it is an actual lens group, not a protective element). It does have a rotational ability that has a slight near-far movement but if you put the new element in the same position the old one was in (screw marks will identify it) they're almost always (99%) right on the money. I've done several dozen and never had to make an adjustment.
There are several lenses where a front element replacement does require recentering (original 24-70 f/2.8, 70-200 f/2.8s, 100-400) and those are not something I'd try at home. The 24-105, 17-55 f2.8 IS, new 24-70, 70-200 f/4 though, are all straightforward.