jQuery double loading in Sitefinity sucks if you're anal about every last byte :) ...
If you follow the documentation though and disable via the web.config sitefinity just goes to hell in a hand-basket because it relies heavily on the RadControls. When it was being developed way back, this wasn't a feature OF the RadControls so why would they account for it.
Solution: Conditionally disable it in your masterpage
The answer is as simple as checking to see if you're in design mode...and then not disabling it.
I've been running like this for over a week with zero issues...it's my new standard going forward.
So clearly this requires a .master Masterpage. It also assumes that you have a RadScriptManager on your page called "ScriptManager1". I assume if you don't you could write up something to find the injected manager and disable it that way.
Note: This will only work for editions of sitefinity running at least RadControls Q2 2012
Cheers,
Steve