I upgraded the standard bluerov to heavy and as the subject said, lost much of the speed and fine control. It seems to be spending a lot of power orienting. It is slightly positively buoyant and a little off center in buoyancy front to back.
I have also installed a gripper and a sonar. I have moved the sonar opposite the gripper to better balance and even out the water resistance.
Even with these add ons, it appears slow. Perhaps moving at equivalent to 25% on the un upgraded version.
I checked the direction of the thrusters, which seems ok. Am I missing something? I almost want to unload the heavy configuration.