I just checked and the front face of the box is curved and ribbed, so that makes it a little tricky. The vent cutout hole will fit between two ribs though and I'd say by adding some silicone around the vent it should still seal.
At present I have no way of automating the freight calculation (in the web checkout) for large items such as the CG-1500 enclosures.
So for now the best way is to PM / email me with your name, address, phone and email details and what you're after so I can work out the freight fairly. Then I will contact you back with the total price before you pay.
I will have the base plates on the web site for separate sale fairly soon.