Beyond version 5 of this router is only supported in openwrt trunk, and not by openwrt backfire (10.03.1). Gargoyle is built against backfire.
Apparently skysurf76 and keyboardcowboy got Gargoyle for v5 working on v7 in this thread
I am about to buy a new router it's either the TL-WR841N v7 or WZR-HP-G300NH2
Problem is that both are not officially supported by Gargoyle, but both are working on newer versions of OpenWRT. A bit frustrating that Gargoyle seems to be lagging OpenWRT in hardware support, but since it's free I really cannot complain.
It would be nice though with a roadmap when the new builds are expected to be released..