notch back rear wing question

[Greg Amy]

my question is where did 28" come from?

GT regs.

where is the the rear edge of the roofline?

Que? Put a marble on the roof and let it roll backwards. When it falls off something, you've found the aft edge.

does rear most body work include bumper?

Yup, 'cause that's the reference plane for where you can locate the wing. (see edit below)

Maybe a photo would be helpful?

- GA

Edit: "...does rear most body work include bumper? Actually, I'd say "no". The intent of the rule is to clarify the characteristics of a hatchback (letting you put the wing higher, thus out of the turbulence of the roof). So IMO -- and I wrote the rule, but please read my sig -- that measurement does NOT include the rear bumper cover.