The 50W PA was originally designed for CW use. For the much harsher conditions of high duty cycle mode operations it should be appropriately derated. I suggest 20-25W. Which is roughly what you will get from roughly 12-13.8 supply voltage.?
However this is a separate question to whether it can be used multi-band or needs band by band bias adjustment; if the correct Class C manual recommendations for setting bias are followed, then this bias setting won't be band dependent.
