I have modified a version of the thread tooltip preview plugin I found to work in myBB 1.6.3. My php skills and knowledge of myBB's architecture is limited, but I was able to get it working and stable. It has been running for a few months on a busy forum (20K + page requests per day) without any problems, so I am comfortable sharing the code now.

Recently I assisted a mate of mine with making some custom modifications to he's Php based myBB forum and I've decided to post some of these solutions here here on my blog.