My only word of caution is to insure that all windows and doors are closed. No one is standing near a slide with a topper with water on top of it when the slide is closed otherwise someone or some thing is going to get wet.
Our three slide toppers always fill up with water when it rains and I leave the water on the topper until we leave with no problems for the topper. Although my wife has gotten wet once or twice when she brings the slides in and we have forgotten about the water on top.
2016 34RL CC; 2008 Ram Mega Cab 2500HD, 6.7L, 68RFE 6 speed, 4X4, Smarty S67