Base on what I've seen and heard, I'm more inclined towards it
being allowed. I'm not sure if I can so surely say, like bro D16Z6
above, that it is "definitely" illegal.
I know some people have discussed that CF bonnets fail to crumple
but shatter instead upon impact and thus it is definitely illegal.
But although that is logical, it doesn't mean it's the stand LTA
takes.
Just like HID. If you buy a DC5R that comes with HID from factory,
it is allowed. But let say you get a DC5GSR with no HID and install
your own HID, its technically illegal. But not logical what? It's
the exact same model of car, just that engine and tranny
different.
So it's best to get an answer straight from them than to base on
'logic' and 'hearsay'. Some logical things may be illegal and some
illogical things are legal.
I don't wish to guarantee you on it, that's why I told you its up
to you. But personally, based on what my friend went through, I
believe CF bonnet is allowed and would use one myself if I had the
money to spare and even bring it for inspection without changing it
back to stock.