Can you not use metal "barrel" clips (they slide over the posts and then you install the emblem and they catch and stay snug on the fender)for your emblems and such so you don't need access to the backside of the fender? I have them and they work very well but i'd do a dry run for proper fit/sizing of the emblems prior to final bodywork and then paint so you don't get into problems with the paint or body after it's done (holes may/may not need to be slightly larger for the emblems to push in without damaging the paint or body).

David