Begin sidebar at body-copy height, not overall content height?

Hi there -- new theme buyer and IMMEDIATELY impressed with the product!

I'm wondering if there's a hook-based way to move the sidebar down so it begins at the same height as the body copy of a post. It seems pretty clear how to do it if I wanted to dig around and hack the PHP/HTML itself, but I'm worried about losing the changes in a future theme update.

Desired final look/feel: Headline stretches full width of the container, as does the byline/meta area. Body copy is then on 75% main column and sidebar starts at the right, vertically aligned on top with the body copy.

Thanks!!