The grille cloth is actually touching the plastic of the horn. It doesn't show because the frame and horn match in profile so well. That tends to keep it flatter up top. The cloth does stretch to a slight curve vertically in front of the woofer, but its hard to notice. I installed it so that it stretches more side to side than top to bottom. Only because the frames are stronger side to side.
There is actually a gap between the end of the port tube and the fiberglass. Only about a half inch though. And the gap counts on my compressing the fiberglass a bit there. Is that a problem? I think that some of my factory JBLs have been like that too.
I used the 1501s because I bought them from the For sale area here on this forum prior to the 2216s becoming available. I think that they are just as good. I could have saved some weight with the 2216s, these are heavy.