halo's are out of the question if you are looking to centre mount. First of all they aren't designed to be centre mounted and it just fucks up the ski. By this i mean it messes up the swing wait and wont be fun to ski. If you want a ski to centre mount, look for a ski that is supposed to be centre mounted. (afterbang, is an example of this but don't buy it because they have awful bases) Hope this helps.
Ps. I think all armada skis are built to not be centre mounted but i recommend the ar7 if you must centre mount a ski from armada.