Is the BEST thing to do if you can't work upper body. Work with intesity and the natural gh and igf that your body will release should help you maintain your size as best as possible.
Don't worry about the oversized legs comment, it is VERY rare for that to end up being a permanant situation. And I personally have never even heard that comment made about anyone other than a limited few pros in the history of BB.
Keep at it bro!