||Not sure if you follow any kind of autombile racing so I will try to give you what I have learned from NASCAR and my ownexperiences. I think that it is harder for a heavy vehicle to hydroplane than a lighter one but under certain circumstances it is quite possible. If the back end ever trys to come around the worst thing you can do is to let off the throttle completely or apply brakes. This could spin you out. I would try to keep the same throttle position and just steer it back in line. In a car I might even give it some gas to help keep the back end from coming around. I know it is hard to discipline yourself to do this but it is important.
If your motorhome handles well in dry weather and windy conditions I think that just slowing down in wet weather is the best thing to do. IF however it does not handle well in dry windy conditions or when big rigs are around then you need to address that issue. Good luck and be safe.