Ok, while putting up the post, I got a hit of inspiration that seems to have worked. I've given the inner container with the text content an explicit height... its own. I'm no longer getting that height bug it seems.
However, if someone knows why the element's height is changing as I scroll, or knows a better way I can do a trapezoid configuration I didn't think of, please let me know. I might have fixed it, but I don't know what I've fixed, and it feels like a dirty fix, so anyone with information would be appreciated.