Been riding mine solo seated all winter- no problem. Even washing (sorry that was before the water shed -ha ha get it)) is ok, the only thing to think of is a slight reduction in security of the tools. I think the tray has a small drain hole which either drips or air dries any residual water that does get in.
Thanks for the reply security shouldnt be a problem basically I only intend taking it off when I go camping solo.I have made up a rack that clips onto the front givi top plate hooks then two stays bolt onto where the grab strap brackets bolt on.So I now have a platform about 2ft wide to take the tent etc but more importantly to keep the weight forward.
Thats what I use it for- takes a heavy and wide load as it is the load point for the pillion, you can adjust suspension etc to compensate. Also convenient to leave the top box in place as lashing required is minimal.
'Alfords do some useful bungies (red) that are easy to adjust the length of. I find they save a lot of faffin about for different loads. They also have plastic hooks so dont scratch.
T T do a toolbox cover £40 made of aluminium with a lock which can be keyedalike if tou have T T panniers, got one on my GS nice fit with plate that swings round to cover the seat lock