Mike it is a bit of a fiddle but it can be done, if you can get a finger into the latch hole.
From memory I had to use my little finger and when trying to do the first side I almost gave up after a few failed attempts and a rising frustration level.
Once I managed to get the backing plate into the correct place and insert a pop rivet I knew it could be done so I persisted until I succeeded. It probably only took about 30 minutes to do the first side but it seemed much longer. The second side was done in around 10 minutes as I knew what I had to do and how to do it.
The secret is to pre drill the backing plates and make sure the rivets slide in the holes easily. My first attempt I did not check this so I could not get the rivet through the backing plate and had to remove it to enlarge the holes slightly.
Also make sure you have everything to hand such as the right length rivets and rivet gun.
Seagrass
