The car you purchased was advertised for several months for $209k - $219k. I would assume you purchased it cheaper than either of those numbers. As I would assume you know, the GTs are very mile / color sensitive. If I recall correctly, your yellow car had near 7k miles. The retail value on that car in my opinion is less than $215k today. Now, having said that, as we all know, the values can go both ways. If it goes up, I'm sure Drews company would reconsider raising your insured value, but at his current value you said he has granted at $215k, that sounds like a fair and realistic number to me. The whipple does not add a lot of resale value ($5k to $8k max if that). I can tell you from experience, as I have helped many people with values on their cars after a wreck or total loss, that Drews company will treat you right in the event of a total loss. If the values continue to rise, I am sure Classic will gladly up your values.
As for seeing similar cars sell for a lot more, please point out these cars. If there is proof of that, I'm sure classic will gladly raise the caps. But from everything I have sold and seen sell, $215k is a very accurate number for a Yellow 05 Ford GT with approx 7k miles. As for your other GT, I don't know any of the details on it, so I can not really comment on that one....