Nah
It would go soggy mate
Now a couple of pairs of knackered springs (not broken ones) screwed to the underneath of an old door (can be removed from house with a screwdriver
) should fit the bill nicely
Or a car bonnet works well if you have a spanner handy
One that worked for me is an old carry mat (camping bed) just pull the end up over your feet when yu sit on it but don't hit any rocks as they are thin and it hurts
Best of all though is to whip the top off a top box (car one ) that is just the right shape
Jason