1) finally, a good spar! several notes here on how I did the work with a shortie bench. note the support under the heavy end, used while working on the outer end
2) Now this pix shows how I fixed my personal problem with not being physically able to stay on the floor for any length of time, bent over the spar, hammering down reivets with a bolt and heavy hammer....I kept trying to fall over across the spar.
Note the white stand under the bench. It supports the Sonex anvel in a small square hole in the bench top. I added two steel pins to the bottom of the anvel to mate with holed in the top of the stand. The stand is 1/4 in square tubing with 3/8 in 'feet' and a 1/4 in top plate upon which the anvel rests. I supportred the spar level forward and aft, and left-right, and at a height to hold the rivet in place for setting with the bolt and the small sledge hammer. It tool/takes exactly three controlled hits of the hammer to set the rivets. I measured each and every one so as to not produce any duds. Of course, i did drill a couple of them out anyway. This system worked very well for my back and knees. it was a $400 experience (parts and shipping dont you know)!
3) A shot of the results looking down upon the shop heads. I think I found a good solution.