Keep an eye on it, last time I did eggs in a bag the bag tipped to the side and melted into the side of the pot above the waterline. Really made a mess of my gormet omlet...
Try folding the excess material togehter and holding it in place with a small binder clip then attaching the binder clip to something up away from the pot/fire.
Like so:
Three eggs, 1/2 onion, salt, pepper, and 1/3 of a summer sausage cooking to perfection.
-Blast