I don't have personal experience with trying it but everything I have read tells me that seam tape won't work for silnylon. Only sealing with a silicone solution will help. Tape and other stuff just doesn't stick to silnylon. Just wanted to throw that out there before you spent a bunch of money on some. If you want to use seam tape, you might need a material coated with a Poly-Urethane coating at least on the side that is going to be taped. You will find that this is the case with waterproof bags and even shelters. For instance, the GoLite SL5 is stated as Silicone/PU 1200mm Waterproof Fire Retardant Coating. My guess is it is a silicone treatment on the outside and the PU treatment on the inside which allows the seams to be taped. Just something to maybe look into...
Otherwise, though, it looks really good. I still need to look into making a few of these should I find the need. Also, you might actually find it useful to have it leak a bit at the bottom to keep the blood from pooling. Just depends on your intended use I guess.