I've got 2 Skyfuns with FPV equipment.
I usually fly them with a 2200 mah 3S 20C battery for the motor.
Then 1000 mah for video.
It can take a whole lot more than that.
Here is a video with all the above and the SimpleOSD:
My guesstimate for added weight is approx 500g.
But the more weight you add, the harder it is to launch.
I've had several failed launches, check out my FPV Fail video, all the fails are with the SkyFun.
It's a real kicker to fly and can leave you trembeling