Great stuff! Thanks for taking the time to write all this up. I'll have to try gluing some plans onto the raw material in future, hopefully that'll reduce levels of wonkiness a bit!

We've been on a bit of a learning curve building EWC from HDPE. Most of the cutting has been done with a bandsaw which is a good jack-of-all trades, as you can cut perfectly straight and square with a fence but also do some curves and mitred cuts. I've also used a sliding compound mitre saw for mitre cuts and that worked pretty well, although it was awkward to clamp - partly due to the relatively small parts, partly because HDPE is a bit slippery.

What're your preferences for drill bits? I'm leaning towards brad point wood drills being better than metal drills as they seem to be better at scooping all the swarf. Holesaws cut really well but the resulting holes are nothing like the size they're meant to be. OK for rough cuts but not for accurate holes.

I did a little bit of work with HDPE using a CNC router and that came out quite well. Although it needed quite a lot of cleaning up (both the pieces and the surrounding area...) the material was very forgiving to work with despite my lack of CNC experience (it would be good to practice on even if you're not planning on using it as it's so soft the chances of breaking tools are reduced compared to aluminium, say).

Another thing that's worth highlighting is that press-fitting things like bearings into HDPE is really easy due to it being so soft, you can make your holes quite a lot on the too-small side and still get things into place.

Barróg Doom is looking awesome so far!