I have the cover but basically, if you want to measure it yourself, the indentations for the cover on each side of the rear interior. The front part look like a D, rear are like a J hook. That's where the cover hooks into when it's extended.
I'm just too lazy right now to get up and measure mine
@Mooseman I have done that but I need a more exact figure, especially after the base where the cover comes out from. My cover is on the way but I need to make a decision on a pricey sub enclosure before it reaches. I need at least 12" between the cover and floor.