I don't think I can change how the signature is pulling the text from the data in your profile. When you view a post - the signature is pulling up data "dynamically" from whatever you have in your profile at that time.
It may be that members are putting the progress info in the body of the post instead of the signature, and then copying from their latest post, pasting into the body of their new post, and editing the latest date/weight. You could also keep your progress info on a text file on your desktop - to update and copy/paste from - if this is easier than pulling it from your last post.
Can anyone who is doing it this way enlighten us? Am I missing something or is this the best way? If anyone happens to have admin experience with PHPBB and knows a better way - please reply here or send me a PM.
Also - I'm working on a custom ticker system for MC followers. Any special requests or input on that would be welcome as well.