The 2005 salary study says a Sabre60 FO makes anywhere from 30-45k with a 33k average. Personally, I'd try and get what makes your QOL good for you and what you think you deserve for your duties performed. The company I work for knows I can fly, but it's how you interact with your boss and everyone else while you're working that really proves you're a good guy to have around and you deserve what you ask for. I asked 45k/yr + benefits for the current 421 job I have and they had no problem giving that to me. That's pretty good money for a 421 flying 40-50 hours a month... well to me it is, but the people I work for are great, we go to cool places, eat good food... it's a blast.
If I were you i'd be asking for 40k at the very least, the worste they can do is say no... and by not asking for what you think is fair, you're only selling yourself short. Good luck.