I always try to use brads, staples, eyelets.etc...because honestly, no matter what the packaging says, I have never found an adhesive that didn't show through..hth
I actually just found a vellum tape runner that was completely transparent. I think it takes some practice to use though as the tape rolled up a little on me, but it still showed through clear. Not sure if transparencies are the same as vellum though.
The tape runner was $10 at a local scrapbook store , but I'm sure you could find one wherever you are.