Project Update.....COMPLETE. The bigger lag screws did not hold. So I decided to go ahead and do the Rivnut idea.
Special thanks to wuck (Pat), he really gave me great insight into the Rivnut project and was VERY helpful.
I decided to use the same tool, the Astro 1442. Unfortunately, my experience wasn't as good as wuck's and I found that the mandrel pieces stripped rather easily, allowing you to set about 4-5 nuts before the mandrel failed. Thankfully they are going to take a look at it for warranty.
Steps.
1. Remove brackets clean off existing gunk.
2. Peel back aluminum skin to see what you are working with. My aluminum tubing seemed to be in a little better shape than Wuck's so I think mine was a little easier project.
3. I started with 1/4 rivnuts to start and slightly enlarged the pre-existing holes to fit a rivnut. Practiced on a scrap piece of metal. I decided to replace all 9 existing holes with rivnuts. I used a reamer and a dremel tool to make as even surface as possible for a good set. I got about 4-5 set and then my tool failed. I did improvise and you can set rivnuts manually using a socket wrench. (I wouldn't recommend this either). Difficult to get a good, even set and had a few rivnuts start spinning. (I'm on the lookout for a better tool). Had to remove a few so I had to upsize, and ended up placing a few 5/16s and M8 size rivnuts. I'm glad I started small with 1/4 inch.
4. Also had to realign a few holes (and drill new holes into the bracket). Once of the factory anchor points was actually in the wood frame, not the tubing.
5. Finally, I reset new butyl tape and got the brackets realigned. It is very sturdy and seems fairly bomb proof. No problems at all using jacks. For the bolts I used 1.25 inch flange bolts. I have a few other screws popping on a few other brackets. I'm going to hold off on that until the brackets seem weak.
Best,
Luke