What are you using to resurface the tanks after you modify them? I have never done a modification that I had to fill in an area. I am going to attempt to remove the 2 fixed hatches and replace them with hatches that open on the front of my HL Tiger I Early. I have the plastic hatches. I assume I will need some sort of putty or filler? Any ideas? Also what is the best way to cut the tank plastics? Hot knife? This will be my first attempt, if it goes well maybe I will attempt more mods. Thanks,