It would probably work with 12.0, but maybe not 11.0. You could just try it and check out the package it creates. I don't see any showstopping, 12.1-specific things, but I didn't really look too carefully. 11.0 doesn't have gcc4, and I notice this line in the SlackBuild:
Code:
TOPDIR=$(tar tf $CWD/$PRGNAM-${VERSION}.gcc4-shared-qt3.i386.tar.bz2 |head -1)
So I think 12.0 is as far back as you can go -- but I'm not sure. They all have qt3, so it *should* work unless I'm missing something.
Try it out -- the worst that can happen is that is doesn't work and you'll have to uninstall the app.