try 26.6 or 26.4 instead?
Cant remember which models, but some I've had were these sizes.
Thank you for your response, Big Cheese. Great advice, as I was fortunate enough to find both a 26.6 and a 26.4... The 26.4 slides in with just a teensie bit of wiggle-room (before tightening the quick-release), and I really wasn't sure if that would be safe or effective. I had to call 13 different bike shops to find the magic solution: A 26.6mm seat post... Fits perfectly-- with a bit of lube it fits snugly, securely, and with relative ease...
I'm not a bike builder, so I've been unfamiliar with this apparently common problem. It's strange to me that the technical specs state that the 1995 GT Tequesta takes a 26.8mm, when in truth it requires a 26.6.
Thanks again, Legrandefromage.