Yes. The heat sinks on it are very substantial.
The little training I had in heat flow guides my thinking and provides general insight, but is inadequate for a proper treatment of an engineering problem that involves dynamic factors. For example, the thermal state in a system (such as the combination of transistors, heat sink, and air) will always tend towards an equilibrium state (heat flow evening out temperature gradients), but a system that is approaching and then in a dynamic steady-state (once operating temp is achieved) requires a higher level of math/physics (or let's just say engineering) to describe properly, such as that indicated in the link that myleftear provided above.
Very nice debate. So the conclusion is, the L profile presence itself influences the thermal transfer more than where it is placed on a heatsink, which has enough mass to distribute the heat evenly. I believe the heatsinks I have should be fine for the amps powered from 19 V power supply, their thermal resistance should be less than 1 K/W, something like 0.75 K/W IIRC. Each board will produce something around 20 - 30 W of heat maximum, which should five me a rise of around 25 deg C above ambient.
I hope you have not forgotten about the insulating gaskets for transistors and thermal paste. You will also need insulating washers for the TO-3 mounting screws.
