As it is raining here, I attacked an unused canister from the kitchen to make a spray deflector for my Elite4. It is not designed to waterproof the head unit, just to reduce the intensity of any water blast which gets past the spray skirts, as I have heard of some units succumbing to water ingress. There are plenty of drain holes around the base, and the cable can go through that large hole on the side. There is enough room to remove the unit if the TI is left in a carpark.
Next project: All-round masthead LED white light for night sailing capable of being hoisted while the mast is up, for thirty bucks or less.. Waiting for parts to arrive