From my brief research, Maryland is probably cheating you a bit to pad their money just a bit.
Your Solstice "curb weight" without passengers or gas in the tank, is rated at 2,860 lbs.
The door sticker is the GVWR or "gross vehicle weight rating" and includes you, the passenge, a full gas tank and a full trunk. I'm not sure if this is the typical amount expected with people, gas and things, or if this is the maximum recommended amount with people, gas and things.
Either way, I am going to guess that the State of Maryland uses the GVWR for the weight classes it uses to charge you for your vehicle fees.
Assuming that, the GVWR of a Solstice GXP is under 3,500 lbs according to people posting here. I haven't checked the sticker on my 2008 GXP, but I will tonight out of curiosity. For all I know, different year cars may have different ratings due to increased standard content over the years.
That said, the non-turbo roadster may have a GVWR less than the GXP. I have no clue.
Maryland seems to have a weight class under 3,500 lbs and a weight class under 3,700 pounds. By callingyour car 3,700 lbs, it sounds like you are 2 weight classes high, because you should be in the under 3,500 lbs weight class, rather than the 3,700+ lb class. Then again, I live in California and have spent a total of 5 days in the State of MD, so WTHDIK? :crazy:
If you are concerned, you could bring your car to the Maryland DMV and tell them to look at the GVWR tag on your car and make them lower your weight class...
The actual weight of your car is going to be well under 3,000 lbs and probably something under 2,900 lbs, unless you own a GXP, than add 100.