l have a general question on fabrication with these materials. I have been welding all types of materials for over 30 years. The more I get into fabricating beams, arms, and cages for Baja bugs I am trying to learn when to use the different materials. I know the basics of strength vs weight. I know for a street or play Baja bug mild steel works fine but as soon as you start over sizing and widening parts it is nessary to use stronger and lighter materials. What information I am looking for is I am starting to work on pre runners as well as going to eventually build a race car for my grandson. In building cages and going from say .120 mild steel to DOM do I use the same .120 or do I drop to .095 to save the weight but is it a strength comparison? The same if I use chromoly can I drop down to .088? Is there a general rule? Is there a chart or guideline to improve the strength and lighten the frame? I have made frames out of 1 3/4 .120 DOM , 1 1/2 .120 mild steel and mixed DOM and chromoly. Any direction or help is greatly appreciated.