: I got an email back from Dyson about fabric, and I think I am
: leaning toward 8oz Polyester since I think it will be a better
: match for the plain polyurethane I will likely coat the boat
: with.

It's a good fabric that's easy to sew and takes finishes well.

: I still need advice on what type of coating to use though.
: I am worried about puncture, abrasion, and yellowing (and cost
: of course).

A gallon of Zar exterior oil-based poly (I like the satin finish personally) will run $25-$30 and give you enough to apply several coats. I find that 4-5 is probably about optimum.

: Also, Dyson recommended plain dental floss for sewing. Is this a
: common thread for SOFs?

Some people like it, but it seems silly to me to mess around with a bunch of short spools of a material that's not designed for sewing. Just go to your local fishin' store and pick up a spool of braided polyester line in the 40-50 pound test range. That will provide enough for several boats and it's cheaper than buying dental floss.