I just looked at those heads and noticed you said a 47 lb bow. I would not suggest those heads for that bow. That design looks like it would actually take a bit more energy than a conventional mechanical head.

If you want to try some mechanicals stick with something like this.

Rocket arrowhead Steelhead line

They used to have a two blade head called Naildrivers, which is what I have used. They penitrate pretty well for a mechanical.

I think you would be better off with something like this out that bow though.

Ultimate Steel fixed blade

I have used these and they kick butt! They fly absolutely great as well. These are pretty decent head for a low poundage bow in my opinion.

Paul