Yes you can. I did this with our camper bed. Here in Columbia, we have a company that will build a mattress for you or you can get any mattress and install in your camper. We had Best Mattress in West Columbia make us a 75" in length mattress. You can solve the support problem by changing the strutts to a high weight. I installed 80lb strutts on mine with the new mattress. Just take off one of the old strutts and take to an RV dealer so you can get the right length and just play around with the weights. My dealer sold different lengths and different weight displacement strutts. Very easy to change. Now I can lift new mattress and get to under the bed.