First up for DIY projects is a favorite around here, the Colorsound Supa Tonebender. It's a Big Muff Pi variant sold under the "Colorsound" brand and distributed by the UK company in the 1970s. The difference between a standard Big Muff and a Supa Tonebender is the removal of the first two clipping diodes and a coupling cap. Seriously, that's it. The resulting sound is louder with tons of thick distortion, much in the same area as a Big Muff, maybe a little less fuzzy, more of a distortion than a fuzz, but still completely over the top. Much more low end than a standard Big Muff. (GREAT on Bass, Keys, Synths, Drum Machines, etc)
PCB dimensions are 81mm x 43mm. It fits nicely in a 1590BB sized enclosure. The layout is pretty loose and that's on purpose. The intention was to allow flexibility with part selection. The hole in the center(1/4") fits the plastic adhesive backed PCB standoffs that are sold on various DIY sites. I see them listed on eBay too. Jacks, pots, footswitch, etc. all get wired directly to the PCB to keep off-board wiring very straightforward.