It isn't the HP it's the gearing. Trany gear ratio as well as rear end ratio, and no they are hydraulic brakes. We only have hydraulic on our 08 SENECA, KODIAK chassis as well as 330 HP and I've pulled 7,000 with no problem and also stopped the load, but with supplemental braking which is required in most if not all states.
PINNACLE 2015 38FLSA. aka: "Roam Sweet Home"