Unstable? its jsut an agp card with a dinky small heatsink, I havent seen a full length card in a LONG time, probally back in the voodoo days, even my GTS250 isnt that long and its heatsink sucks up an extra slot (as big as your face!)

And pc makers havent included those grooves since who knows when, I know its a cold day if I see those full length card holders in a ATX case, and even with my old AT cases it was pretty rare