Thanks again guys,
The mats in the canoe are a medium density foam (they sell them in squares that lock together to be used as flooring in caravan annex and the like) not sure on the weights of them but the four of them you could hold on your pinky finger. I keep using them for two reasons, the first stems back from when the canoe was brand new and i wanted to protect the inside, but the real functionality of them is that when a little water gets into the canoe (from fishing or excited bow paddlers) all my gear doesn't get wet.
Sure does seem to be a great forum. The level of respect, comradery and engagement is very nice to see and to become a part of.