I'll add this tho doubtful it helps the OP who is probably a better rider than me. But since the topic is posture related I hope you don't mind. It might help someone else? I read (& I try to follow) that to get the best posture for riding a road bike w drop bars one should ride with their butt sticking out (or, as if you were). For old guys like me I can't straighten my back (prone) that much, but visualizing it this way helps me get my back straighter. It does feel funny at first but then I get used to it. When I ride by store windows I can see that I am not sticking my butt out. I don't ever ride with elbows on bars tho on some of my longest rides I was tempted.