You might consider replacing the mattress rather than a topper. We found a 10 inch mattress set (4 inches Mem Foam, 3 med foam, 3 firm foam) on overstock and went that route. Could not be more pleased with the result. $299 delivered to my door and more comfy than the bed im my house...

. Another pluse is you canadjust firmness by switch the order of the standard base foam layers. Weight has not been a problem for us. I truley think you could add rocks to the factory mattress and still be more comfortable than stock...