I have accidentally discovered the minimum speed you must go in order to keep dry with the roof off. I was driving on the motorway with the roof off, and then it suddenly started raining. I remained dry because I was doing about 60MPH. The traffic ahead started to slow down and then I found the minimum speed to keep dry. If I go below 50MPH I will get wet, and if I do about 55MPH A few little drops of water may get in but I will stay mostly dry. So I recommend not going below 55MPH to stay dry. This accidental test was done in light to medium rain and my sun visors were rotated upwards in the wind deflector position. Oh and your height may affect this slightly, as I noticed that the wind deflector was a little bit wet, so if your seat is far back you may want to do over 60MPH to stay dry.
