I just got a good deal on a barely used Claytor small fly (thanks freakflyer!!). Even at new prices it seems like a lot of tarp, in terms of weight-to-price ratio. It is however more like 22oz. rather than the "1 lb" as advertised on the site, once you figure in tie-outs and the stuff sack. Putting it more OP coated tarp realm. My teeny Integral Designs 5x8 Siltarp and/or Silponcho I had been using as flies, are 8oz. and 10oz. respectively, tieouts sacks and all. So I may stick with them for backpacking, and use the big one for carcamping. Or modify my load philosophy. Test hang this weekend.
Anyway, the question was, does it need to be seam sealed? It appears to be made of 2 1/3 1-meter sections.