Okay, thedoctor. I'll just answer your question here. So mylar is obviously lighter. But the extra difficulty is not worth it unless you can build your helicopter at least .5 grams under the minimum requirement stated in the rules.
Tissue is great, however you will face issues with warp. Extra humidity will affect the tissue, and tissue in general is easy to rip. It will weigh more than Mylar.
The best material I have worked with, which I learned from Jeff Anderson, is produce bags. Try to find the flimsiest ones, and the ones with cool logos
. I believe these are in the same range as heavier tissue (I have no evidence to base this on), but are suitable for many teams. Unless you are at the national level, or have a 2+minute helicopter, I doubt it would affect your performance much. Produce bags are much easier to work with than Mylar and can be applied using very similar techniques.