As far as using rondo, it has its ups and downs. I still resin the part before I rondo, so that the rondo won't flex and crack. As far as using it inside with the fiberglass (mudglassing) i wouldn't do my parts any other way. Its the best way I have seen to harden a part that is cost effective. As far as using it on the outside, it has its ups and down. Its a bit faster than just bondoing, but it is less uniform to work with and gets messy fast. You really have to plan the areas you are going to pour and how much rondo you are going to use. That being said, it worked great in the areas I used it on!