Eureka!
I've been fretting for weeks over how to set the rivets on the narrow ends of my rudder and elevators. I bought a "no hole" squeezer yoke from Avery which was good for a few of them. Then I got a relatively narrow tapered bucking bar from the Yard Store which took care of a few more. I was still left with a couple I couldn't reach at the very tip of each part. I've been advised to give up and use pulled rivets but, since I'm not going to close off the ends of the parts for awhile, I decided to sit tight and see if something comes up.
Today after seeing this thread I went to Home Depot and check out their axes. There was only one that looked like it might work. It was about the right size but it was a little bit on the narrow side and had a slightly concave shape to it. Still I figured it was worth a try since it only cost about $20: a little more than a bucking bar. Axe in hand, I headed toward the exit but stopped at the tool section as I often do. I checked out some various roofing hammers and the like hoping to find the perfect shape. I was about to give up when I noticed the chisels right next to the hammers. The shapes of the chisels seemed better than everything else including the axe. Not only that but I had several chisels at home to try. I put the axe back where I got it and left without buying anything (for once).
Sure enough, the chisels did the job! I just put the last three rivets in my right elevator. I covered the edges of the chisels with some masking tape to prevent scratching the ribs. Two of the rivets went in with no trouble. The one in the very narrowest part caused a bit of headache. The rivet bent and I had to drill it out. In fact I drilled it out three times before I got it right. I looks decent now and I think it's set ok. Better and stronger than a pulled rivet I wager.