Ok, just measured it. It's actually only 1 mm of play. Still too much in my opinion. I read another post somewhere and someone had suggested running it and seeing if there is wear on my backplate, if all seems ok then it should be fine. I think I'll just try running it.
But that won't happen until I work out how I'm going to fit it in, another post for that tho. Ah rc cars, love it but hate it.