Agreed. If I could be bothered going out to the garage I could actually weigh my spare bonnet. They are very light, usually lighter than CF, which often cracks over time, especially with the bonnet being opened more often that your regular road car. Most over here are running stock bonnets over here unless running the Stillen SC.
I'd say why not go for the 350 as a track car. We have a number of heavily worked and full on track 350's over here, and they run competitively, in a number of race series, both track and full Targa cars, if you look to that direction and get serious about it. You will get the odd breakage, that's the nature of racing, and if that's a major concern, then racing probably isn't something to do. Sounds like R00ner is pretty keen to track a 350.