Questions: self drilling/ tapping screws for chassis work

Lots to think about here! I may have to do some experimenting on scrap metal to find my comfort level. The hardest part will be finding high quality screws -- the stuff carried by the big box hardware stores is sometimes of lower quality.

Ductape, your comment about corrosion is interesting, since I plan to use (wait for it) duct tape as a barrier between the steel and aluminum.