Looking forward to this build! Will be crazy if this thing still has the grunt at just 2:1.

2mm steel definitely is a deathwish. Pretty much 2mm of anything is a deathwish, save maybe high grade ti. We had I think 4mm steel on the front of our machine for the champs, and after just two fights with the spinner that came 6th (Inertia XL) it was literally like a piece of lettuce. Useless. You're more or less limited to Hardox, titanium or very thick plastic (HDPE works well) these days.

We also happened to use 6mm chain for our weapon and I'd say don't bother, if you can avoid it. It will work, but it stretches an alarming amount (you'll most likely need more than one tensioner), and getting it on and off is a huge pita, we found. We are going to move to "HTD" timing belts. I have good word that 9mm wide HTD5 belts work very very well for drive and spinning weapon transmission. Here's one source of many in the UK: http://www.beltingonline.com/5mm-htd-timing-belts-4575 - payoff in being lighter with the aluminium pulleys, too.

Keep us posted.