..OK, so tell me or give me your opinion ....
Can you run multiple transducers on the back of your boat without interference
and more to the point .... can you put a Lowrance unit on one side and a Hummingbird unit on the other side and both function properly.
I am looking at going to HB graphs but really don't need to get rid of the Lowrances that are currently on the boat unless it would cause issues.
I am not a BRAND guy so I do not care if both brands are on the boat.
Just interested in the functions of both

I have a buddy that is running a Lowrance HDS12 and a Humminbird Helix both at the bow. Their transducers are both mounted at the back of the boat, and there is no interference.

Depends, if you are gonna use both brands for di and si your gonna have to run on different frequencies. If you go with the mega that shouldn't be a problem other than pitting the transducers far enough apart to where they impede the si beams. With 2d you may have to run the lowrance on 83 and the Humminbird on 200 since the Humminbird is constantly pinging the 200khz for depth. Just all depends on what you want out of the setups