We are getting very tired of a mattress issue. We have gone thru our dealer, Heartland, then a mattress dealer several times. They have sent me a replacement mattress 3 times. I only weight 250 lbs. each time it only takes one or two days and you can see a dip in my mattress. What is the weight requirement for the mattress? Or how can I get a updated one? This is in a 2017 Prowler.