Has anyone thought about making E/G molds out of HDPE or UHMW PE plate? I have access to a 24x48 CNC router and I'm thinking I could achieve around 0.005" positional tolerance with decent flatness on all surfaces, maybe better on reference surfaces. One or two 4'x8' sheets of 0.50" HDPE at $100 a pop should be enough to make a decent mold and it would be reusable. Obviously wide spans would need to reinforcement to avoid sagging under hydrostatic pressure, but other than that the only major issue I can see would be the heat generated by the epoxy curing possible causing the HDPE to soften. The liquidus of HDPE is listed at ~260 F but the glass transition is something like -100 F so I'm not sure how it would act under the temperatures generated by the epoxy. I haven't read the entire E/G thread but I haven't seen any discussion of HDPE molds in what I head read.