First, you might change to ANSI 25 instead of 35 if you have chains and you can make the change. Second, watch out for steel. Some applications will require steel, but in most cases, find an alternative - aluminum is the choice of FIRSTers it seems. When you put things on your bot, always ask - can this be thinner or shorter? Chances are, the answer is yes.
Also, get creative! Go on down to Home Depot or Lowes or Menards for you Midwesterners. Look around and see what they have for you to play with. You'll find strong aluminum tubes that are very light and relatively cheap. You'll find things like wire mesh, PVC and wood - all of which can replace aluminum and lexan in certain applications. Just make sure you get the light stuff (i.e. NOT oak). Last year 1020 had two pieces of 30"x50" light weight wood on the bot. It weighed almost nothing and just before weighing in, we hit them with a couple hair dryers to get rid of the moisture
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Congrats to all on completing your bot (or sorta completing as is our case) and good luck in competition.