I tend to only do short, steep climbs standing - raises my heart rate too much. Although I love to stand together on the tandem. And if it's a longer ride, I'll just spin instead to conserve energy. For exampla I only stand on Diablo on the flatter section just before the Summit to stretch before the final climb if I need to. I don't even stand on the 17% section.

To answer the question asked I actually have my hands on the rounded part of the drops when I stand and climb. Weird huh.

V.