In massive amounts they are extremely laggy: I doubled the part count on one of my shuttles from 200 to 400, and I wasn't even finished the shielding! I would only recommend it for small crafts. Also, if you get a screeny with all the tiles exploding, I'd love to see it! They are mass-less, but that might change in 1.0. I use them sometimes to form a pointy nosecone with all three antennas. glad to hear it!