PSP allows you to remap the buttons for PS1 games. Not all games require all 4 shoulder buttons.
When I played FFVIII via remote play I had the same problem but I later found out about the remapping and I believe (not sure) there is a multiple button scheme (e.g. use of alt or shift in PCs) to circumvent the problem. I have never tried it as I stopped playing FFVIII and started suikoden 2 which doesn't need shoulder buttons.
SO in short, I believe there is a way to do it.









