CI grill/griddle Pans
I recently started looking for a stove top grill. I wanted a reversible two burner size. After doing a little research I found that most people didn't like the inexpensive aluminum ones so I looked at cast iron. If you have looked you probably know that the Le Creuset double reversible is about $170. Sorry I didn't want to deal with the extra hassle of plain CI. Anyway in case anyone's interested I found a clearance sale on the LC reversible single burner model for $60. After trying one and liking it I bought a second. While there is a ridge where they join, it hasn't been a problem. A couple of trade-offs to that inconvenience are that you can have one griddle up and one grill up at the same time and since each one is lighter it's easier to clean.
I have no connection to the supplier. In case you're interested it is cutleryandmore.com
Let me understand this please: You are joining two square (single burner) grills together? Are you just pushing them together, or have you actually joined them?
Assuming you are using two pushced together, that might be a problem for some cooktops. Mine, in particular, has a bridge burner that heats the space between two burners. If there was any kind of space for oil or meat juices to run down, such as when grilling something long and flat that normally requires a double burner, it could burn badly when the stuff runs down onto the burner. If you have to disconnected burners, the chance of this happening is probably less.
Join can also mean bring close together as in 'joined in marriage'. I think I mentioned reversing one to have a grill and a griddle. I have two burners (front to back) and the grates are level with one another so it works for me but probably not for you.
There is a raised edge on both sides to catch oil/grease but I supposed it could overflow under some conditions.