I'm currently in the process of drawing out plans for a new panel lifter/flipper design, but I wanted the machine to be rather compact. I was looking at around H - 8cm L - 15cm W - 12cm but I'm not entirely sure whether that would be to compact since from what I have seen, a lot of bots at the weight class are much longer than this.
Doesn't matter about the dimensions so much if the design is something you are happy with. :P

Would using this be more protective than HDPE or polycarbonate? I know that the bot will not be fighting for a while, but I feel like I want to slap together something I feel will work and then work from there.
I am on the fence. I certainly think it'd work in what you are planning to use it for but then again, admittedly at a different weight class, I found angled polycarbonate to work just as well. HDPE is very energy absorbing though.