Re: [rendezvous] Rock Dragon as canopy
You might try doing a search of this forum. TM posted a good review of the Rock Dragon a while back.
My short opinion: if you are in Australia, go with the Rock Dragon over the Troll. If you are in Europe, go with the Troll over the Rock Dragon. If you are in the US, it depends on where you live.
In my opinion, Rock Dragon has less penetration and a bit worse glide angle. But, I think it has better openings, and is a bit more stable in deep brakes (and allows steeper approaches).
It might also be helpful to look at what your mentor or other experienced jumpers in your area are using. What they know, they can provide more help with.