Hey why not just get the Pro cfw instead? It has popsloader and iso/cso support built in. You can get it here: procfw - X-Generation Aftermarket Firmware for Playstation Portable
Since you're on 6.20, get that version and run the proinstaller then the pro620bootloader and it loads the cfw automatically...
Or try the TN-E Hen (fix?) floating around out there I think the popsloader was a thing he fixed in it.
Anywayz I didn't have any problems getting the PSX2PSP games running on Pro. You aren't trying to run the original PSX iso, are you? If so that would be a major hassle ... just look up some PSX 2 PSP iso's.... (isozone is good if you can't find it on torrents)



Hey you know how you run the HEN from your games list and it reboots into CFW? You could do a dual boot kind of deal, where you install Pro and then you could either run HEN or the PRO quick launcher, ya know ... But I did run into an unrecoverable problem when I was doing it that way and had to reinstall OFW then the CFW ... well it's an idea if you want to test it out ... just don't tweak too many settings in it