I made mine 300x300 with a few mods. Direct drive extruder, tri-wheel for z and y axis, eccentric nuts for x axis, 24V PSU, and 120V bed. Thanks to spauda01 for all the documentation!
I noticed that your D-Bot kept the original design's partially cantilevered design (as opposed to the alternative design (for a bed size 300mm in the Y-direction) which uses four rods/guides for the bed. I am looking to use a similar sized bed, and I was wondering if there are any issues (especially at higher speed prints) with vibration that you experience? Thanks.
I haven't had any problems using the two guide rods with my 300x300mm bed. I definitely had to add support to the overall frame. I printed out some extra connectors for the corners and I am considering doing more. I also used a direct drive solution which adds more weight to the printhead and adds to my vibration. Another thought is to make the bed 300x300 but shorten the Z height a bit. I find that I don't usually use the whole Z height but I definitely use the X,Y space. Shorter Z height would give better stability. Good Luck!