The plans are for Weld-On 10 and not Sikaflex. That could make a difference.
Also, I don't recall a thickness being mentioned. It mentioned using washers to shim under the windows if needed - until they were flush with the cabin top. Mine sat proud as it was, so I didn't put any washers down.
Other than that, the only reference I found in the plans was "thin coat" without any prescribed thickness.
Phil