When I saw the title of this topic, I knew I had to give an opinion. <img src=icon_smile_big.gif border=0 align=middle>
Now if I can only think of something to say. Well, that's not usually too much of a problem.<img src=icon_smile_wink.gif border=0 align=middle>
First, I wouldn't increase poundage just to shoot mechanicals. Draw weight should be something you can comfortably handle, as well as one that matches the spine on the arrow you're shooting. I'd go with a fixed blade, just because I'm not a big fan of mechanicals. If your draw length is anything less than 28", I would definitely go with a fixed blade.