Most all upper level aerobatic planes use foam sheeted wings along with tail-feathers and other items. A Carden kit has boxes of foam included and the 40% ones are over $1,000.00 today. They can be a little heavier than built up wings however some builders are able to make the built up wings come out heavier. Once you learn how to construct a plane with foam covered parts it will shorten the building time for most builders. It also makes for a wing that doesn't have dips so the airflow is smoother. A few smaller planes use this construction. Global's sticks are foam wings and they used to make a little pattern ship called the Hurricane that has plug in wings on aluminum blades that flies quite well. I find fully sheeted wings to be easier to cover as you can put the joints where you want them and not need to plan color schemes over the open framework. I wouldn't hesitate to get a plane with this kind of construction. RCM (magazine) has an article about lightening foam cores in the December issue if you want to read further.

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