Don't transmit on HF with another antenna with the Drake connected to whatever you put up for it.
Risk of FET damage? It does have dual diode input protection built in. i think I read of a 30V RF rating on the front end. But, yes, I do xmit with 1kw using different Drake equipment and a different dipole that will be only 30 feet from the new SW antenna. Likely the new SWL antenna will be a sloper, rising to some 40 feet towards a locus tree.