If you want stronger rivets, especially for tunnel extentions and structure work the absolute best way to go is with driven rivets, not pulled.
Pulled rivets are hollow and nowhere near as strong as a driven.
Here's the driver...(Chicago Pneumatic, cheap but worthy)
http://www.hansonrivet.com/w80b.htm
You can actually get away with the cheapies that most auto parts stores carry for body work.
Practice first on a blank piece of aluminium before turning yourself loose on your tunnel though.
I've done many extentions on mine and friend's sleds and the results with a driven rivet are very professional. It looks like it's stock!
And yes, HUCK brand will last long after we are gone. Best puller available