Two buttons for one on gamepad...

[LunaMoo]

/Moo
Using control mapping you can set for one button/key to activate few different psp buttons at once, you can also set multiply buttons/keys to activate same psp button, you can't however set those keys to be required as pressed at the same time to trigger it, so simple answer - you can't exactly do what you want. You can however swap analog axis with d-pad which I guess was made exactly for those tiny limited pads. Just go to Settings->Controls->Control mapping and assign some key to "Axis swap" whenever you press that key it will swap whatever keys you have set to d-pad&analog.

Note that lots of psp games already have pretty weird anti-human controls and nothing really replaces a full size gamepad, not even real psp which genuinely sucks in comparism;p.