Preventing a pool in my cover?

Well the last few days it has been pouring in dry AZ and I have probably bailed out about 500 gallons of H2o out of my boat cover. Thank goodness I just bought a new one that doesn't leak. Problem is I have a tower and I bought a cover that wasn't specific for my boat or tower. it works, but its baggy. What do some of you guys recommend to try and prop it up so I don't get huge pools of water? I heed to be careful so I don't put a hole in it. I was thinking of trying to make something out of PVC. Any suggestions are greatly appreciated by my back.