Thanks for the many useful replies. A few responses -
-- re-scoring - I'm a little skeptical about re-scoring. I was taught in stained glass class that a single score is best, re-scoring tends to mess up both the score and the cutter. I don't know if that strictly applies here but I have scored and snapped a lot of glass, and many thinner tiles, without undue problems. In short, I think the scoring is fine, I know how a good score feels, sounds and looks.
-- dowel method - I'll try that and see how it goes. Sounds like it might work well as long as the cut is close to the middle of the tile; might be awkward if the cut is way over to one side.
-- wet saw - sounds like I may need to do that after all. I like the idea of laying the full tiles first, saving all the cuts for the end. I do have an HF and borg stores nearby so I might look around and decide if renting or buying is better. I am, as others have mentioned, learning as I go. That has worked for me before.
-- having the store cut them - I'm not sure the big box offers that kind of service, but I will ask next time I'm in there to pick up some more tile. I'm doing the job a little at a time as time permits (and to spare my back).
-- hardwood clamp jigs - that sounds like fun, I might try that too.
Thanks, -- H