Last season with 1293, we started Palmetto about four pounds overweight. We went to two pounds underweight in one day with a few changes.
Anybody familiar with 1293 is familiar with the team's love for 1/8" aluminum. The hopper that year used a lot of it, so we initially cut large holes in it and filled those holes with garden mesh riveted in place (and painted, natch). When that didn't cut it, we took a slugbuster (a hydraulic device for putting round holes in things, in this case with a little hand pump) to it. Ultimately, we had the hopper remade in a Fix-It Window using thin-gauge stainless steel, which we then re-swiss-cheesed. The end result was plenty durable (even for blocking shots--sorry, 1676), but far lighter.
Similarly, we could've fabricated a lot of things differently with 1618's robot this year. Paper is a terribly underrated material--we're using it for our graphics, with a few extra numbers printed up as spares. On
the arm, the numbers are backed by a piece of cardboard. Sure, it might not be particularly heavy-duty--but it'll hold, and replacements are cheap and plentiful. Similarly, we picked pegboard over metal for our electronics and pneumatics panels--they're cheap, easy to mount to, and light as beans. If we needed to drop weight (which we don't--ten pounds under FTW!), we can get it cut with nearly anything.
Oh, and don't count out the kit wheels either--they're nice and light, and are roughtopped with relative ease.
And, if worst comes to worst, never be afraid to ask around for advice. Odds are that someone at the event will have some tool or part that will knock a pound or two off.