What is the voltage drop across a TIP41c when it passes 2.9A for long durations?
you might be trying to do this, in principle. However, not quite suitable for power level, just showing the shunt regulator configuration.

Next, here is how to do constant current with the 317 regulator, again in principle, probably not good for 3A directly, although the TO-220 packaged 317 has some power capability