Try chmod 755
To give some hope, I have userfilter (usually disabled but sometimes) running in PCLOS & Gimp 2.8.2 but this is a 32 bit system.
Got it some time ago from a debian package, so it can't be a very complicated plug-in.
It is always worth a quick search and this came up for a 64 bit rpm
http://www.lefred.be/?q=taxonomy/term/72&page=1 right down at the end of the page
http://www.lefred.be/files/gimp-plugin- ... x86_64.rpmMight be worth a try.
Might be best to unpack this and have a look. To unpack I use the command
rpm2cpio something.rpm | cpio -idm
Even unpacked it's a tiny file so I have zipped & attached it.