I'd recommend going for a mask/head mount as I found fitting it to the barrel you tend to shoot a lot at the floor.
The curved mounts fit well on masks with somewhere to affix it to, but I used a gopro vented helmet mount to strap it to the top of my mask. I have some i4s arriving shortly and I think I'll be using a gopro headband that I bought but I'll have to advise how this works once the mask is here.
I use a gopro when I play, like El Delementez, I've found that using the barrel mount I shoot a lot of floor, Thats not so much of a problem for me in short games as my marker will always be up, but in longer games like north vs south im less concious of where the camera is faceing.
The mounts that come in the box (adhesive ones) will fit most masks if they have a flat surface available. With my i4's that won't work though because they're too rounded so I use the headband mount which fit's nicely and I find gives me better footage
I prefer it on my barrel as it is easier for people to see what you are shooting at and you dont end up just haveing the back of your hopper in the shot, while playing north v south I just used it on my barrel as it is also alot easier to see when it is turned on and recording and not recording , also on your head it means you gotta get lower down to not get shot in it, as when ever I see one popping up thats my target.