Yes it is. I don't ride the bike like an R1 and have never had a moments concern with it. It was always designed to be perfect on gravel roads with knobblies when I personally don't think overbraking is a great idea so I was very happy with the set up. The bike has always had TKC80s on it and the combination seems fine
Raidxtreme who built the bike always said try it and see. They could offer a second disc (presumably on the other side !) or a larger supermoto size disc. Personally if I was keeping the bike I genuinely wouldn't see the need to change it as the bike suits my riding style. (And we have close family experience of a car driving twat pulling out in front of a relative with horrible consequences)
If however you ride 2 up a lot and like to leave your braking late going into roundabouts, then I would probably do for the second disc.
But in view of our family experience I wouldn't sell a bike that I thought was underbraked