Update: The FS3X works fine on the first two switches, but the third is a combination of #1 and #2.
I am using scripting in Gig Performer to detect these MIDI events, but it won't work directly without some tweaking.
Hope this helps.

Thanks Rob. I have decided to buy a Digitech FS3X 3-button pedal. The first two buttons work as expected, the third fires both #1 and #2 together. Obviously MIDI-wise there is a slight delay between events. I am primarily using this with Gig Performer, so I am working on a workaround script to detec...

I'm looking to get an FSX-3 myself.
It's just a single TRS jack, but I don't know if ME will detect it properly.
I am getting it via Amazon so will have a play and get back to you, if it doesn't work, I'll just send it back.

I am aware the MIDI Expression can detect a double footswitch configuration, and the few that I have found are stupidly expensive, so I am looking to make my own.
Does anyone know how they are wired for the software to detect it?