I was going to move mine, having read stories about how covered in crud they get.. but when I got there (changing clutch at the rime so the airbox, battery box and everything else on that side of the engine was already apart) I couldn't see that mine was particularly being clobbered, so I left it.
I dunno if everyone else is just running around Commando. My beast has the undertray and both the lower wheel arches in place... so only the back of the gearbox lets the weather in.
Silicon hose is slightly softer than the regular PVC tubes... so if you're not sure about the size, go for the smaller option that you think it could be. It'll stretch without too much force.
Ralf S.