Ive been looking at this.
Milhouse (i think) has neons installed so he be able to tell you how he has attached them, but i cant believe you have to drill the floor pan that would be nuts!
As for attaching Rear one, is there no where to attach it to above the rear height of bumper,if not id get some very strong double sided Tape of some sort (not double sided sticky tape ) and attach to inner part of rear bumper, with a peice of string tied round it and tied to peice of body work. So if worse did happen that it came off, it would just dangle until u noticed or u noticed drivers laughing at u.