I don't think anyone would make you replace it... not sure about having to look through it though. I'm 6'2" and have never been able to tuck enough to not see over it. Try it out - you'll know for next time.
I race in 600 Production and 600 Superbike in AFM. Almost anything goes in Superbike, but would you believe the rules specify that I must have a stock windscreen in Production? (Oh, but internal engine mods are OK!!! WTF!!!) Having said that, I'm continuing to use my Zero Gravity clear double bubble in both classes. It's a minor hassle to swap it out, and besides, no one is going to file a technical complaint on a guy that isn't in any real points contention. Especially for a windscreen. LOL.
EDIT: Hmm, I just realized that your question probably is in reference to trackdays, not racing. Anything goes, non one is going to make you swap it out for a clear one. However, I would agree that a clear one is preferable (to me at least).