I have a generic side mount off of ebay but I think they are all similar. I hate it.
Comes lose every couple of shots making it impossible to zero. I even drilled the mount and added another screw next to the original screw to give it added stablitliy but due to the fact it uses the small plate on the side of the reciever to attach to which isnt a tight fit to start, it seems flawed by design.
I heard the b-square has a top screw of some type too to reduce the movement, making it much better than a lot of them but all things considered, I would just go with a top mount.