The peak on mine is the most inflated area, up to 18 inches. This is on a large house, 32 by 54. Stretching the PVC tighter on the second covering didn't flatten the peak much. Along the sides the inner layer bulges in but the outer layer is almost flat against the bows. Mine ranges mostly from 6-18 inches air gap. I couldn't change that much at least not tighter.

The most surprising aspect of your situation is that the peak isn't inflated. That could be from begin too tight but may just be the geometry of your structure.

I made mine tighter the 2nd application and feel that wasn't best. It seemed to result in small holes developing at the points where the PVC was most stressed. This was enough to deflate the covering and I had to patch the holes. If you think yours might be too tight I'd loosen it a little and see how it looks.

Also don't over inflate. At least that's the official recommendation. Just enough inflation to keep things from flapping in high winds.

my blower has a round cover over the fan box , it can be opened for more air or closed for less air.

Or the blower is not adequate for your size GH.

Mike

For double poly greenhouse roofs, optimal air inflation pressure is 0.25 inches of water column pressure during hot weather, and 0.45 inches during cold and/or windy weather. A simple homemade water manometer can be built to check the pressure.