find out what the mount points are for the p1 card and p2 card. (i.e. the f:/ drive and k:/ drive) make sure you increase the timeout for the machine from the default 5 seconds to 15 seconds so that way it can fully save the catalog.xml data onto the card. i recently made a bug fix for this with an old itg3 theme and it works pretty well on my local arcades upgrade cab. we are running a personally fixed version of oITG alpha 8. i rewrote how it worked and its a hell of a lot faster than even beta 2 or even beta 3 is. but enough about that
i dont know alot about dedicabs, but i do know when the .ini files are messing up everything
if you use a custom theme, make sure the line MemoryCards is set to 1. I noticed when i didnt touch it before that it was set to 0 for some reason. also, if it has a weird subdirectory like itg3 themes do, include that into the importsubdirs line. that got my theme working with cards perfectly. but seeing how we use a usb hub on an upgrade cab, we cant set the p1 and p2 card ports correctly without causing problems with the hub we are using. that shouldnt be a problem with a dedicab though, as it is preset for that type of port layout.
hope this helped. saves should work after this and if you had any signature failed crap, itll fix that too.
best of luck.