I ended up doing the panel upgrade after all because my 200 amp main service is a split bus bar with a 100 amp max branch breaker. They upgraded it to a 225 amp square D so they could plug in a single 200 amp breaker and run it to the GW2. The additional cost for this upgrade was $4200. At least they didn't surprise me with it after the fact....although it's now been two days since final inspection and I haven't gotten an invoice yet