Does anyone have a boilerplate jury "if you believe one witness beyond a reasonable doubt, that is enough to convict" instruction?

That is certainly a correct statement of the law. E.g., Lee, 206 S.W.3d at 623. But, I would be hesitant to ask the court to so instruct the jury, as it might easily be considered a comment on the weight of the evidence. E.g., Kirsch, 357 S.W.3d at 651-52; Morales, 357 S.W.3d at 5-6. To me, the safer approach would be to object to any argument that implies otherwise, and carefully craft your argument. E.g., Grantland, 146 S.W. at 197.

^^^^!!!!!

Don't do it. I would also worry that it violates Paulson's holding that we don't define beyond a reasonable doubt.