Would this be a good idea for my GSA?

Walking around dressed like a member of the opposite sex will not give you a single clue what it's like to be transgender. You know you're not and that will negate any "feelings" you have toward the situation. You will likely be ridiculed as a drag queen and not someone trying to explore what it's like to be transgender. Your safety would be an issue. Heterosexual teenagers can be the worst examples of humanity when it comes to inclusiveness. You would likely have a lot of problems using the women's restroom (if you're a man dressed as a woman) and will likely be assaulted if you enter the men's room dressed in drag. If you want to document the feelings of the transgender population, interview a transgender person and have it published in your school paper.

Actually, there is a book by Norah Vincent titled "Self Made Man" in which the author (a cisgendered lesbian) tries to understand men by taking on the guise of one for a year. She ended up suffering from gender dysphoria (even though she never actually calls it that) and it took her months to recover from the experience.

That a really nice idea, but I would be worried about your safty and possible leagle issues with the rest rooms depending on where you live. Have you looked to http://community.pflag.org/Page.aspx?pid=194&srcid... for guidance on gsa programs.