I have my mod installed by a "professional" (can't help it with soldering!) on a v7 and it loads everything-PS2, but it seems that it doesn't boot most PS1 games. Most of them are originals of various regions, I have more than 80 titles and only about 20 of them can boot. Mostly I get an infinite black screen and sometimes the "Insert a PS2 or PS disc" message. Forcing the PSX/DVD mode didn't help at all.
Note: I just upgraded to 1.88 (from 1.7x) and the problem remains the same.