I second the BIQU external board solution.
It removes a large portion of the heat loading from the controller board.
It is cheap insurance and works great.
Try to mount it where it will get at least some airflow if possible.
If you are using an "SSR", be absolutely certain that it is a DC output type, and not an AC output type.
If it is an AC type, in this application it will turn on and stay on until you cut off the power to it.
That would cause your bed heater to overheat, possibly to the point of destruction.
But the BIQU mosfet will work perfectly (I ran one for a long time before converting to a mains-powered bed heater).