Unfortunately this type of hacking isn't really sustainable. Even small tweaks to the Gmail UI often change the DOM in very unpredictable ways. When they released the new compose feature, pretty much every single Gmail Chrome extension broke.

We haven't really announced it yet, but I've been working on a new email platform with some friends to solve a lot of these issues. It's essentially Rails/Meteor for email features, and lets you skip past hacking Gmail or writing a full IMAP client.

It's called Inbox, and we're aiming to open source it in January. Ping me if you're interested in playing with it early. :)