Wow! First off thank you for your wonderful replies!
Well, after reading your posts I don't think he's very underweight. I should have taken a picture of him when I first brought him home. I suspect now that he was much more dehydrated than anything. I post a picture I took today. He was fed yesterday. He's 23" long. I seem to have misplaced my scale but what I'm hearing makes me think he's gonna be just fine.