I'm using the metric Summit ones, 3" long but with my wheels, they don't stick out at all.
I did have trouble find the right wheel locks, because of the length. I wanted open ended ones but the people at Gorrilla are idiots and only refer you to a local shop who says "duh...???"
I ordered the right conical ones from Summit and ground off the ends to make them open-ended. They are tack welded to the hub/stub axle from behind.
If anyone's using Kyokugens, I hear the splines for the locks wear out or the keys brake easily, many complaints. FYI.
Owen