Expected that closing the elevator leading edge would go as smoothly as the rudder but it was not to be. Ended up doing it in three seperate stages and despite creasing the outer skin in the same way I had with the rudder, I ended up with a very untidy close. Fortunately it will be hidden from all but the most nosy inspection and it is certainly mechanically sound - just doesn't look as good as i would have liked. Still not sure what I would do differently to get a better result.
Ended up buying myself a pneumatic pop riveter. Makes pop riveting a breeze. Wont get into all the tight corners, but where I can use it, I certainly will.