Actually George, If the .016" elevator and rudder skins are done per the plans, they don't tend to crack. The biggest cause of the cracks are caused by the trailing edges not being folded enough. If the skins are folded so that you have to open the leading edges to insert the spar, they work just fine. Mine, and many others, have been flying for 14 years or more with no cracks. No sealant, no extra ribs. Just built per plans. Even after the parts are completed, the trailing edges can be crimped more with careful squeezing with seaming pliers. Not saying that the sealant and extra ribs wouldn't help. Just haven't seen any evidence that I need them.