Rmag,

If you look at your 6 shot gun, you will see that the flutes are in the "meaty" part of the cylinder, between the cylinders. And the stop/locking notches are in the top of the cylinder. On a five shot cylinder, the notches fall in this "meaty" part.

I would worry less about fluting, and more about the amount of material between the bottom of the notch, and the inside of the chamber wall. If you look at a lot of pictures of grenaded revolvers, they seem to let go at the notches to the left and right of the back strap. I know I have seen a lot of blown cylinders where the top round is sharpnel, and you can see the two on either side of the top round.

Craig