Oh I know: I've seen plenty such pictures. I'm more worried the Labs might bully him!! He'll be the smaller of the two unlike in your picture here. He can't even swallow a small pellet in one go yet. (He eats them with relish btw. I didn't even have to try.) I know there's always a risk one could nip at the other or vice versa but that's very broad. I'm hoping to get some specific info from somebody who has kept the two together. Yes, I know he won't stay small forever but he doesn't look like he'll be doubling in size within a month either. I can always rehome the Labs once he gets a bit bigger.
So to clarify: I'm asking about a temporary, not permanent arrangement.