With both Epic and silnylon it isn't practical (cost effective...) to seam seal tents because it has to be done with the tent assembled and it takes up to 48 hours to dry. (visualise a tent run of 100 (US made) to 300-1000 (China made) tents all set up for a couple of days)
A way out with silnylon is to put a PU coating on the underside. Tape will stick to that. The problem with doing that is that at this point you will need to dry your tent because PU will attract mould. In the long term it will perish (see "sticky tent fly" threads)
Knowing this but still taking into account the advantages of silnylon over non impregnated versions, more manufacturers are using it. For example Macpac from NZ with the 2010 tent range. (yes, they are shipped with a tube of silicone)
Franco
BTW, I have been doing some experiments with wet tent fabric.
After several hours of steady rain a silnylon fly gained 25% in weight, a fully wetted out polyester ripstop 60% and a partially wetted out (shorter exposure) gained 31%.
With silnylon most of the extra weight was in the wetted out guylines and the rain drops that accumulated during the folding (all done in the rain).
Next time I will do Epic but knowing that it can completely wet out I wold expect a considerable difference between dry and wet storage.