I have a similar issue but got resolved.
I have Radtech ScreenSavrz which is similar in function and form factor to the Shaggy with my 11" MBA. With just the ScreenSavrZ, the 11" MBA closes normally. However, with the ScreenSavrZ + keyboard protector (mine is Moshi Clearguard 11 but the result should varies little for other keyboard protector), it doesn't close properly. However, since I use Radtech SleevZ and once the MBA gets inside and when it is taken out again, the lid closes during the process.
As a recall, the 2010 11" MBA didn't seem to have the same problem or my memory could be wrong.
So basically my ScreenSarvrz is crushed during the storage of the MBA and so it is not an issue. I was concerned about wearing the hinges but the chance is slim as if you close the 11" MBA with nothing inside (i.e., screen protector and/or keyboard protector), there is already a slight gap which I think is designed to avoid the keyboard from accidentally in contact with the inside of the screen.
To be clear, I can close the lid of the 2011 11" MBA normally with just the keyboard Protector (mine is Moshi ClearGuard 11) or with just the Radtech ScreenSavrz. But with both, I have to leave them inside a higher sleeve and after a while, the lid closes properly.
I now see the Shaggy one has a thickness of 0.6mm for the Air whereas the Radtech ScreenSavrz has a thickness of 0.5mm for the Air (and their Pro version is 0.6mm though). So unless 0.1mm makes a difference and then the Shaggy won't work..