Ah, perhaps some of the 'kits' are waterproof then. I had asked a seller a while back and they said no its a straight copy of the plastic hull.
The Asiatam hull is metal inside with a plastic outer, it has torsion bar suspension though making it on par or near to the Tamiya set up. Plus has screw free access to the hull internals and a decent mounting plate for other gearboxes. However you have to get Asiatam wheels for it, its hit and miss fitting others.
Commanders hatch on mine was a bugger, solid with glue like yours I guess, had to run a knife round several times with a lot of force until the inside lip gave way. Managed to remove that from the outer and re-attach before glueing the hatch section in correct place. Might be worth getting inside the turret and pushing up on the inside hatch section top if you get me?! Good luck!