For anyone with a PSP that would like the perk of being able to switch to playing with the classic DualShock controller from time to time you're in luck. Acid Mods have found a way to do exactly that.
Acid Mods has a full step by step entry as to how to do it, as well as a nice little video. The mod itself is just hardware modifications, so this can be done to any PSP.
It doesn't matter what type firmware is on it, if you have the skills to do the mod, your PSP can handle it. The mod is nice and clean, it just has a controller connector placed right above the power switch. Which will leave your PSP still looking as sleek as it did before.