piCorePlayer - error when uploading custom-convert file

I'm experimenting with some custom convert settings and prepared a suitable text file with what I need.

When I attempted to upload it using pCP's "upload custom-convert" facility, I got the error "Invalid file format, must be a text file".
No matter what I tried, couldn't get it to work.

So as a tempoary measure, I manually created custom-convert.conf in /usr/local/slimserver and restarted LMS.
That worked: the settings were applied as expected.

But as a permanent solution, I wanted to check something with the experts here.
I note that /usr/local/slimserver/convert.conf is a symbolic link to /tmp/tcloop/slimserver/usr/local/slimserver/convert.conf
Should I place my custom-convert.conf inside /tmp/tcloop/... and create a symbolic link to it?
I'm speculating that a reboot of pCP might lose the custom settings unless I get it right.

PS. I'm using an old pCP (v4.1.0), so perhaps that might be a factor in the upload not working?