Hello. Thanks for your review! I personally don't have PSP 1000 but people from PSP discord community tested it and reported that it works fine. Sadly without the device it would be hard for me to determine the reason, but it's not about memory capacity in comparison to PSP 3000.
Hi! Update to my previous comment: it now works on my PSP 1000. Apparently, the data was copied incorrectly the first time. It's strange because it didn't say "FILE CORRUPTED" or anything like that, but something didn't copy correctly, so it wouldn't get past the loading screen. Now, after copying it again to my PSP, I was able to test it and it works perfectly on my PSP 1000.