Hi Shok I was recently asked something like this on my rcwarbirds advisor column. The problem with just adding to the wood is that you leave the wood vulnerable. just like moneycoat adds strength to the wood it covers so does a layer of glass. for instance a sheeted wing. if you add moneycoat it adds strength as it helps it hold together a littl better in a crash or even helps to make it harder to punch a hole in the sheeting. by adding a layer of glass cloth when you glass this will add the same kind of strength. if it is just a control surface remember there are open bays under the wood so still a chance to be damaged. if you put a layer of .5 oz cloth down when you put your few layers of Poly U on the controls you wont be adding any thickness to worry about any more than you would add putting you several layers of poly on. remember poly is paper thin when going on as it is as thin as water to apply already and not like epoxy which has a lot higher viscosity (right word?) so I would go that5 way but if you want to just use the poly U it will work to give you a paintable surface but remember it will be weak and prone to breakage.

Joe