Here's my report so far:
I've got working - Circus Lido, Psycho Chaser, Soldier Blade & Tongueman's Logic
Not working - Cyber Core, OutRun (4 roms tried), Parasol Stars, Ninja Warriors (2 roms tried).
All these non-working roms run fine in an emulator - can I assume that there's something bad in the rip that stops it working on a real PCE?
Also, is it likely that th utility to remove the 'SNES' header could be removing something it shouldn't?
Because some are working, I am hoping it's just a ROM thing and the hardware is fine. My main reason for getting this is to test out homebrew games on real hardware anyway.
One thing I can't get working is US games on Japanese Duo, tried swapping and not swapping the bits with no success - only tried Magical Chase and China Warrior so far, white screen both times.