On the subject of spinners; I've so far found it's much more important to design a robot that can survive a fall from 15 feet onto solid ground than can take a spinner hit; there's only the championships and one or two other events which allow active spinners to fight; the majority are all just featherweight melees where the Heavyweight floor flipper is your main enemy :L I've been hurled into the arena ceiling a fair few times by that thing (and also thrown around by Explosion and Flow to name a few) and driven off fine, whereas I'd likely be toast in seconds if I came up against a spinner (my armour is only 5mm HDPE). You should be fine with your 10mm HDPE though, just need to make sure it's all held together fairly well.

By the sounds of it once you've got your wheels you should be well set to build a fairly solid little feather