Whoohoo!
I just tried out wiring a non-jamma Mr.Do connector without any soldering - and it works perfectly!

I used a db25 printer cable, stripped enough of each wire to thread through the eyes of the jamma connectors and twisted them as tightly as I could. I shielded them with a small length of 1/16" shrink tubing and used a hair-dryer to shrink the tubing and tighten up the connections a little. I did this for video and power, enough to test out the method.
The printer cable's wires are pretty thin, but it seems to be enough to carry the video signal and the +5v and +12v from a power supply. I plugged the printer cable into a db25 data switcher (like
this one) to see if it could be used to switch between PCBs. I checked everything with a multi-meter and all connections seemed to be going strong.
I hooked the whole lot up and powered on. I switched the data switch to Mr.Do and as if by magic, Mr.Do appeared on my monitor!
Tell me there's something wrong with this set-up; nothing ever goes right for me first time