Which type? Plating, encrusting? One of each? Dont know if it makes any difference or not, but it may help. I wouldn't see why not! Same species, should be fine next to each other. I've seen people intermix the plating. I have 4 different color plating monti's very close to each other. Two of them actually attached to each other. I had to thin them out and separated them a long time ago though.
I am actually planning on doing that in the 180. putting all the plating monti's in one area and letting them grow around each other. Hopefully it works.