The most important thing is to place them where they won't be in the way of your paddling. I recently put two flush-mount rod holders on the gunwales of my Pescador 12, much like the Viking yaks have. I was careful to put them far forward enough so my forward paddle strokes didn't hit my rods. If I put outriggers on my yak, they would have to be pretty far aft, to clear the back of my paddle stroke.
I was paddling once, and Fil Spencer(kayak guide) came past me and said "Take long strokes!" I started doing that, and soon, I caught up to him! You need to keep your paddle stroke areas open to long strokes, and you'll make more distance per stroke, and not tire out as fast.
Island Jim, resident Old Fart
I'm an Eighth Day Adventist. On the Eighth Day, God went fishing!