Why did you get a +1" set up?
Also, do your Mancini spring hangers have 2 bolt hole locations for the spring eye bolt? Which one are you using? Because if you're using the lower hole, you've probably raised the rear of the car.
The springs should settle some if this is the height when you just installed them. The other thing is, a 225/60/15 is a pretty short tire compared to a lot of the drag race based cars that are running a Calvert set up. Most run larger, and much taller, rear tires. Which will change what that gap looks like.
