I used to go up that road on a regular basis, so always managed to stay below the limit, but then I genuinely do try to do that, even when going to work at 04.00 and there is little on the road.
As you say, it’s dual carriageway, so can easily lull users into straying the wrong side of the limit.
The camera I don’t like is the one on the west bound carriageway of Millbrook Road, just past the Millbrook flyover.
It’s positioned just where cars are trying to switch lanes to either get to the M271 or Totton, via the Redbridge flyover, and those trying to squeeze into gaps can be caught slightly above the limit. Plus the camera is completely hidden behind a big road sign, which I thought was illegal.