Working on my -8 empenage I found I was unhappy with the results of the close quarter rivet puller style dimples. I also didn't want to pay almost 30 bucks (although they are very nice) and wait for shipping for a Tight Fit Dimpling Fixture from one of the usual suppliers.
This was my solution to the problem and I'm incredibly pleased with the resulting dimples.
Total cost for this tool (not including the dimple dies I already had) was about 50 cents and took about a half hour to make. Another plus is that you can change the dies for different sizes. If you want to make on yourself here's what I did.
1.5"x4"x3/16" scrap steel
Mark the center whole of one of your close quarter dimple dies (included in most basic RV kits) near on corner of the bar leaving about 1/8" on each edge. Center punch the mark. Drill a 1/8" (or whatever bit you have thats convenient) pilot hole. Using a 1/2" drill bit countersink a hole in the plate until the wall of the countersink is approx 1/16"-1/8" deep. Check dimple die fit in the countersink and countersink deeper as desired. Use a file or grinder to round the corner and edges. Debur/buff with scotch-brite wheel.
I'm sure other people have come up with similar methods but figured this might help some people avoid some downtime.
Enjoy and keep building!