Oh man, I must be half-sleeping-zombie-mode today.
Place the .elf in the ps2 folder, or both it and data in the same folder.
I rebuolt the zip anyway, should work now, sorry :-(
Anyway, there is some problem with joystick jumping, I do not know what happened (I did not touched much of the input reading since last time, that was working. I plan to release more betas than planned, to fix those nasty stuff I found after the beta4.