These are the three that I've tried my damnedest to beat to death, they really are like a Timex
Damn, I just hate the idea that all three will outlive me, and I have no valid reason to ever buy another PV!
I haven't built a DNA-20 box mod, but I've made several boxes for my own use. The carto tank in the background of the pic is on an OKR-T/6 mod. Here is a PDF of how to build one for yourself.
http://www.howder.com/dena_howto.pdf