We have a Big Horn 2008 3670RL. We love the trailer, but wanted to have a different mattress for the bed. The bed in the Big Horn is a King Size and the one in our home is a California King. The California King is a little wider and longer. We will be retiring the end of this year and wanted our Ca King mattress in the trailer. The mattress is solid rubber and a wonderful mattress. So-----we exchanged the 2 mattresses. Now, when we attempt to close the slide-out, the mattress is too long. There are about 3 inches that need to come off the CA King mattress. Any Suggestions on how to shorten this mattress?