Straight vs. double offset back rivet set

I'm about to rivet my top skins and have been planning to back rivet them. Consequently, I bought a 12" straight back rivet set from Cleaveland which they said should work just fine. However, except at the forward-most part of the main ribs, the angle I'd be holding the back rivet set at is pretty severe and don't think I'd be smashing the shop heads very square. (Since the -9's wing is thinner than the other RV's, this is more of an issue.) Avery, on the other hand, sells both a 12" straight and a 12" double offset back rivet set that would, presumably, solve this problem. Has anyone who has used one or both of the two types above comment on how they worked out?

I'd really like to back rivet the top skins if possible, especially because my wife is a little scared of using the gun. With the back riveting, all she would have to do is hold the bucking bar tight against the skin.

Any thoughts appreciated.

Steve

Back riveting wings

I helped my son back rivet his 7A wings - used the Avery double offset tool with great success. Even in the 'flat' areas, the double offset puts the tool more square than a straight set would allow. The riveter has to be careful to keep the tool aligned, but neither of us had trouble doing that.

Dennis Glaeser
7A wings - will be using that tool on my wings soon!

I used the Cleveland backrivet set on the fuselage top deck with good success, but for the wings, my wife used the swivel rubber guarded set and I bucked the rivets. They came out very nice using that method.

I used the Avery 12" double offset set for the ribs and J-stringers except for the rib/stringer intersection rivet and those rivets near the aileron bellcrank bracket. I used a regular 1" set and a long bucking bar for those rivets due to the tight confines.
Notes: (1) Due to the geometry of the set and the tight spaces torward the rear spar, the gun angle becomes quite pronounced. Normal riveting methods might work better here. (2) Do the skin-to-rear-spar riveting after you move the wing assy to the bench. Else the riveter lies on the floor and you'll like the appearance. (3) The 12" set uses so much energy that I used about 65 psi with my 2x gun.

riveting the outboard skin,
Steve

I bought an offset back rivet set to use on my wings and didn't have very good results. I had a hard time making decent shop heads. I ended up using the swivel rubber ringed mushroom set and a bucking bar like Andy Karmy did. Every thing came out fine.
Jim Wright RV-9A 90919 wings Arkansas

Thanks for all the (conflicting ) suggestions. I'll just have to pick a method and try it.

Steve,

I did the first wing by back riveting and the second by top riveting. I can't tell the difference. I did think top riveting was easier. The trick was to have the person with the rivet gun hold the rivet set to the skin with their free hand. To reduce dents I used a flush swivel rivet set.

IMHO, the guy holding the bucking bar is more important than the person with the rivet gun. The bucking bar I used were these tungsten bars which allowed me to get into all the small places. They weighed in at just over a pound each and work great!

Thanks Steve, Jim, and Bill. Knowing that you used both helps. Likewise thanks to everyone else who posted a response. I'm probably going to save myself $29.00 and do it the old-fashioned way.