The Source: The heat seems to be coming from the right side radiator vent.
There are two radiators on the GS, one on each side. The right side has a coolant temperature activated fan that sucks air through the radiator and belches it out the vent. To a lesser extent, the catalytic converter and exhaust pipe produces some heat that may contribute to the issue on the right side.
The Flow: Air enters through the right side radiator and exits via the exhaust port on the right side of the fuel tank. The radiator fan is mounted on the back side of the radiator and helps the movement of air from the radiator to the exhaust port. The intention of the design is the heated exhaust belches out of the port, which is the widest point on the right side of the motorcycle body, and into the open air.
A significant amount of the heated air that exits the radiator exhaust port is sucked into the area between the right side pannier and back of my thigh and lower leg. This area is a 'dead' space with almost no airflow created by the forward movement of the motorcycle. It is relatively calm and the hot air just accumulates, heating up my leg. The fact that the cytolytic converter and exhaust pipe is just inches away contributes to the heat accumulation. These elements are well into the airflow along the undercarriage of the motorcycle
I rode with the pannier removed to see how much it being in place contributes to the heat accumulation issue. There was a slight reduction in the noticeable heat sensation but not enough to make a big difference to the comfort level.
Defining the Problem: Heated radiator exhaust air accumulates in the area between the right side pannier and the rider's right leg.
A simple test, to confirm that it is accumulation of heated air, is to deflect airflow into the 'dead' space. At speed, with the cruise control engaged, when I stick my open hand into the airflow away from the right side and deflect air it into the 'dead' space, the sensation of heat against my thigh and calf goes away as soon as turbulent airflow reaches my leg. It doesn't take much deflected air to change the 'dead' space flow dynamics.
The Solution: Deflect ambient airflow into the 'dead' space to create enough turbulence to disrupt the pool of accumulating heated air.
I fabricated a piece of thick plastic sheeting to fit in the bush guards around the bottom of the right side cylinder head. It is fastened with plastic wire ties. It has the effect of scooping air and deflecting it into the 'dead' space when the motorcycle is moving.
Initial tests rides have been good. It works well enough to reduce the accumulated heat in the 'dead' space from distractingly annoying to barely negligible. I'll keep working on the solution to resolve the 'comfort stress' issues associated with the new watercooled GSA. Given its new design, I am resigned to a certain amount of issues that challenge my farkling abilities. Hey, on the bright side...it will be great in the cooler months. All I have to do is snip off the wire ties and remove the scoop until the hot weather returns.
The scoop is made of thick, flexible and strong plastic cut from a yard leaf bag frame. Source: "Lawson Products - Easy Bagger"