I have struggled with this with my 14 foot cat for a few years now. It is a hard balance finding a center rowing position with a passenger. My longer cat seems much more versatile as far as weight distribution.
As far as the front kick bar, I did have a couple of close calls with feet getting pinned between the foot bar and rocks when I was pin-balling in technical water. To install an actual seat off the front bar required a pretty long bar, and more exposure.
If the passenger is sitting on a Paco or cooler, they have a low center of gravity, which is preferable I guess if only running whitewater, but not great if fishing. It also puts the feet lower to the water line and closer to rocks, etc...
I had a short experiment with putting the passenger behind me, and that was a safe haven for the passenger, but I could not get used to a forward rowing position.
What I finally settled on is a fixed slightly raised seat about 12 inches behind the front bar with a short kick bar off the front bar, which does not drop nearly as low.