When playing the PSP Slim on a TV, does it fill up the whole screen or does it gives black bars? If so, is there a option to stretch the image to make it bigger?
It plays at native resolution, so yeah, there are 'black bars'. AFAIK, there's no way to change this on the PSP, but if your TV can zoom, you can do that to get around it.
black bars. It's due to HW limitations. When you do TV out for the bios/movies, the actual thing is running a 720x480p framebuffer in vram. Durring games it cant do this since games use vram in different ways. Very sad sony did not put a small hw scaler chip so the vid out was done by it and not cheaply done in the hw. Btw, some homebrew apps do support full screen output (not refering to psp games, i mean like emus).
can you have any control over your homebrew games regarding interlace or progressive? Because the PSP can only display games in progressive mode, but the rest of the stuff can be seen in interlace too.
Homebrew can do interlace as well. Again the problem stems from the cheap way sony did video out. When in interlace mode there are two framebuffers in ram, one for even scanlines and one for odd scanlines.