Welcome to the site. The boat is a classic design. Anything that stays around long enough is going to need repairs. I'm living proof. My transomcap was made of plastic but my transom was solid when I replaced the cap. If you let water intrude and then have 400lbs hanging off it, flexing I would imagine it would be a weak spot with any boat. Have fun you'll enjoy owning a V20. Here's a link to my cap redo.
http://www.wellcraftv20.com/gallery/album50
Again welcome! Billy Mac