I try to NOT operate any boat which doesn't have forward controls & that are forward where you can see obstructions/hazards in the water.
(My "bigger" skiff has an 18HP electric-start Johnny for power & my homemade "stick steering".)
Center seating should move the center of graviy (CG) far enough forward to negate the few extra pounds of weight of a 10hp over a 5hp engine on the transom?
Another string of thought is - just how much of a faster cruise speed (not wide open, but cruising) is a 10hp over a 5hp? Is the time saved worth the extra weight and fuel? Only you can make that judgement. I ask only to have you review it. Sometimes I've talked myself into somethings that I thought would be better, only to find out that I'd tslked myself into paying twice as much, and getting only 15-20% more performance. (Boats, planes, cars, and women can all fall into that Baliwick).
To be honest, I've slso found the opposite to be true - in some circumstances. I recall a knife after which I lusted. But - oh! - it was expensive. A "similar" knife cost much less, and was supposed to be just as good. So I bought the chesper one. What I found out was that I patted myself on the back only once - the day that I bought the cheaper knife. But, every time I used it, it was unpleasant, and I kicked myself in the rear.
Theoretical hull speed for a displacement hull in knots is 1.34 times the square root of waterline length in feet. The caveat is that the 10 Hp is more likely to get you on plane which dramatically increases speed for a given Hp. Once on plane I believe that speed factor varies the cube root of the Hp, so It takes 8 times the Hp to go twice as fast ( 2 cubed = 8).
General observations: Right, a boat that is planing is no longer performing as a displacement hull. Is this boat hull one that - with only 10hp - can be powered up out of the water? I've had speed boats that would plane with a 12 horse if lightly loaded. But a pirogue is not usually a planing hull, I didn't think.
Doubling your speed with a land craft, water craft, or aircraft does generally take 4-8 times the power. A first step is often to reduce weight and drag. They're usually cheaper to do, up to a point. Often, more power (usually a bigger, heavier power source) requires a stronger structure to both hold the engine, and withstand the additionsl stress (some more weight). That path often hits a point of diminishing fairly early in yhe game.
F'rinstance, my aircraft is basically 1930s technology - aluminum skin, round hesded rivets, windshield raked back only a few inches, support struts under the wings, antennae sticking out of several locations, etc., etc. Modern aircraft made of composits both weigh kess, and are more aerodynamically ckean, therefore much less drsg. Roughly, they cruise about 50% faster with the same horsepower and fuel burn rate!
Water, being a more viscous fluid than air, msy afford similar or expanded possibilities?
Growing up 100ft from Grand Bayou, us boys put all kinds of motors on all kinds of boats. I drove an 8 ft long 36" wide stepped hull flat boat with a 9.8 hp Mercury. Yes, it did plane, and then some! It kept up with 25 and 30 hp motors on "normal" sized boats. To get it on plane, you had to gun the throttle with the friction hold on and step to the front of the boat, when the bow finally came down for two bounces, you'd step back and grab the tiller again. Did I mention we were young and stupid?
The common boat you would see when I grew up was a homebuilt 10-12 ft wood or 10-12 ft aluminum boat with a 10 hp motor. They planed very well with two adults.
A 10 hp outboard on that little boat will be a lively, little racer........ unless you're a really big fellow.