I really like the open belt look on this particular bike, showing all the Silver. Covers are going to make it look heavy and clumsy. Personally I would have made a fairly tight fitting stainless strap over the front of the front two pulleys.. like a flat mudguard if you like. With minimal visual impact.
I think there is a good argument for leaving the belts uncovered; if a stone does get under a belt it is very likely to be spat out after the first revolution and probably only go round one pulley. However a foreign object in an enclosed cover cannot escape and could be moving at speed and ping into the belts several times.. furthermore it could well go unnoticed unless it made a lot of noise and continue to deteriorate in a damaged condition, whereas open belts are immediately inspectable and any fraying or holes will come to light very soon during one of those longing looks (don't deny it
).
emzedder had a nasty experience when his balls dropped, and his belt tensioner bearing broke up too, which is more relevant! I know that the bearings are inside the belt loop so the balls are fed into the pulleys to some extent, but I can't help thinking that many more of them might have dropped away into space if they were not enclosed.
Happily emzedder is a very sensible chap and noticed the damage before a belt failure.
I have a vague recollection of someone conducting a test on polyurethane drive belts, when they first started to become popular.. They were feeding gravel into a Norton or Triumph belt conversion and failed to damage the belt or pulleys, just to prove a point over chains.. Cam belt is a slightly different scenario, I agree, but I think they take more punishment than we think?