I didn't work on the airplane yesterday, but I was determined to work out this riveting issue. Well after experimenting a little I realised two things, I had my air pressure too high (I had checked it last session and turned it down, but somehow it creeped up and 5-10 psi makes a big difference) and I had better results when using masking tap on the end of the rivets set like for flush riveting (gives the set a little grip on the rivet head to avoid smilies. I am very happy to have this worked as it really slows my progress when I get frustrated.
Also I actually worked 4.0 hrs this morning, but I chopped up the entries to allow more detailed entries.
Here I am finishing up the left flap brace rivets.