by pleasewrap » Wed Jul 24, 2013 3:11 pm
A lot depends on the specific Darlex material (thickness, stretch, etc.) used for the sack and the way it's put together. If it doesn't have internal sleeves, then it's really more for show than for bondage - there's just nothing to keep you from moving your hands around to undo the zipper. If it has sleeves, but a lot of give to in the material, you may eventually be able to wriggle an arm out of the inner sleeves and then get loose. Darlex has a decent amount of stretch, so this could very easily be the case.
If there's no inner sleeves, then you really have to be well restrained before going in to the sack.
So if she wants to be sure you aren't going anywhere, some rope or straps across the chest, elbows, wrists, or wherever else she likes would be a good idea. You can get some decent nylon luggage/cargo straps from luggage stores, hardware stores, etc. without breaking the bank. It could even be fun to start without them on and then have her add them slowly over some time while taunting/teasing you if it does have sleeves - just as it looks like you might be making progress...
We have a neoprene one and even with the give in that material, you aren't getting out once you're in the sleeves, zipped up, and the ropes are tightened.