I like a nose grab BR and R2R, You can really poke it out and add some steeze to it. I think a melon in a lil easier to grab. The trick to not going R2R on a grabbed BR, I try and trow it more over the top,(like a reviser cartwheel, and a R2R more out the back like a normal backroll.) How ever you grab it make sure you get it right off the wake or you will never get a soild grab. Good luck They are both super fun tricks.
Here are 2 pic of my nosegrab R2R
Photos by Walt
Here is a nose grab backroll
Photo by Scott
Photo by Walt