I love the Gladiator fin and use one in my 12'6" Glide.. But.. they like to go straight and track.. and they make foot steering harder.. If ever I'm surfing my 12'6" I use a dolphin shape fin..
IMO if you want better foot steering you need a slightly smaller fin than a Gladiator type fin.. One with less area in the base of the fin.. and one that's a little more upright (vertical in shape and less rake).. The stock fin that comes on the new Naish Glide/Javelins is one of the best that I've used to improve steering..
You need to borrow and try a few for yourself before you buy if you can.. I'm no Ace expert so maybe others here can give you better Ace fin advice..
Here's a vid for you that I just came across..