lowering convertible top questions

My 64 has the original top and rear window. I'm slightly paranoid about preserving it as it looks fine and doesn't leak! It's a manual top and the first time I lowered it, it wouldn't go all the way down so I picked it up slightly and carefully pulled all the material out between the metal frame members. I also unzip the plastic window and lay it flat in the well.
Your 68 should have a glass window so you're good there. If I were you, I'd lower it half way, stop, and pull the material out between the bows.