Referring to your comment on the other thread about no one answering this one. It could be that no one has done it yet. Take a small piece of the grass mat and be the first to give it a try, post your results to inform others how your experiment worked. All the great ideas these folks have started with an experiment somewhere in the history of the hobby.
Good luck,
if i put a stream or pond or somthing with the water gel on a grass mat can i roll the mat back up with out messing up the water?
if you need more spacific detals: I'm using a wodlansecnics large spring (spring color) grass mat.