evincent220Good question. The poly is actually sil coated on the outside and PU coated on the inside (for a non-slippery floor and so the fly can be seam taped).
Repair tape doesn't stick very well to sil, but it sticks pretty well to PU so you can use tenacious tape on the inside of the fly and likely many other tapes.
On the outside you pretty much need to use liquid silicone as sort of a glue. You can apply straight silicone (e.g. silicone caulk from a hardware store), or dilute that with mineral spirits so it paints on easier to fix small damage. Likely the easiest is to buy it pre-diluted from a gear shop as a product called SilNet.
If you get a rip you could tape it on the inside and then lay a bead of silicone on the outside (giving it time to dry). For a larger cut you could use silicone/Silnet to glue on a patch using a scrap of fabric. For example, you could sacrifice the stake sack and cut a patch out of that, and then glue it on with SilNet. Note that you'd need to glue the slippery sil side of the patch on, so you're gluing sil to sil using sil. This is basically what TarpTent recommends for fixing their sil tents.