[jman4747]

Well for one I don't worry too much about difficulty of machining as anything I get would be sheet metal thicknesses. As for safety, zinc dust, steel dust, aluminum powder, all can be harmful and you take the same precautions for all of them. Ventilate and protect your lungs. I doubt they like aluminum powder.

Also on weight, personally I've not had a problem. Our 2012 bot (photo attached) was 109. Our robot this past season (a 4.5' tall FCS with a 10pt climb) was 98lbs at inspection. We needed to add weight.