If you trust your test setup for 17.4 GHz to be within a few dB of what you'd get at a certified test lab, sure. Yeah leaving the stub is bad practice because

If you trust your test setup for 17.4 GHz to be within a few dB of what you'd get at a certified test lab, sure. Yeah leaving the stub is bad practice because it could cause you trouble in FCC certification, not because it always will or even probably would. Let's put it this way, if you wanted to get enough energy into your fifth harmonic to be within 10 dB of what you were putting out on the fundamental by leaving a stub like that... you would tear your hair out for a good long while before giving up.