With your tank being made in 2003, you don't need to worry about re-certification. Just get it filled and get your ass grilling. The tabs you have on the side that hold the tank may be somewhat adjustable. I cannot remember exactly, but I know PBE Gummi mentioned that they were adjustable to me. I'm still looking for a tank. I can say with 100% certainty that a 20lb tank will NOT fit under there with the charcoal bin in place.
while you are enjoying the grilling session, keep an eye out for a curb grill. any of those cheap ass Fiestsa grills will have the new style OPD connector. Remove the regulator asembly and take the OPD connector off at home and then screw it into your regulator. The tank already has the provisions for it. One thing, when you need to get the tank filled, you will most likely need to go to an AGA or other industrial gas supplier as most refill places won't refill the small tanks.