The way it was explained to me is, there are two weights targeted.
150 class, and max weight. The weights in between are all mistakes.
Nowadays , mid to high 160 weights seem to be preferred in alot of discs.
It does seem strange to me that they can mold a Candy Valk at 150 grams, but not at 160.
My lowest Champ is a 167, exactly as you said, but I do have a seriously overstable flat 161 gram disc in Star plastic that I can rip as hard as my arm will bear.
I do have to mention one thing though, I'm old and weak and 350' is a killer drive for me, but, my 175 gram Champ Valk flies farther in a neutral wind than any of my other Valk discs with my weak little arm, so Cindy, try a heavier Champ Valk, it might fly good for you too.