[thefro526]

We have never had our withheld parts weighed upon entrance to any regional I've been to in the last few years, but it changes depending on the regional. (We've also never brought more than 10lbs or so in with us anyway.)

That being said, if your withheld parts appear to be close to the 30lb limit, someone may ask you to weigh them just to be sure, or another team may tell the Inspectors that your parts should be weighed...

Depending on your mechanism, you might be able to pull some COTS components off like Chris said, or if your mechanism has some relatively simple parts, you could bring in the raw materials and make those simple parts on site.

(Also, you might run into someone at your event that has read this thread and knows that your parts have a chance of weighing over 30lbs and they may recommend that the parts get weighed...)