I've been trying different materials and the best I've come up with is a cotton handkerchief--pure white cotton, washed many times first. I cut the hankerchief into strips a tiny bit wider than the length of my 801 carts. I do this both with a roll of the cotton and, as someone suggested before, by folding the strip accordion fashion. I try to use as little as possible and the strip ends up being about 2 inches long before rolling or accordion folding. It provides good wicking, holds a lot of fluid but doesn't leak, shows no scorching or burning and has a good clean taste. So I'm going to work with this for a while.
The paper towel (and other things like that) bother me because this is highly processed paper with a lot of additives, bleaches, etc. I imagine some of this could vaporize out with the heat applied to it.
This forum is very helpful. Thanks, folks.
Wally