Haven't tried running anything via OPL in my entire life, but I can add it to my own testing list later down the line. (You'd be surprised by how many platforms I tried running Tales of Phantasia on before Cless released the demo patch)
No guarantees that anything will change just 'cause of that. However, I was under the impression that at least on the PS2, launching things from USB storage would always be a troublesome compatibility affair if the game streamed lots of data.
That would be much appreciated, but just remember to defrag your drive of course

. To be honest I was quite skeptical @ the whole idea of OPL running games off an external HD through USB, but most of my games work great! The only catch is you need to check the compatibility list and loading screens take a little longer. (usually just those colored screens are the only slow down, but once it loads it's usually never lags!)