I have a twin XL which is 38x80 and need to use small pillows on the front edges to keep it from moving forward and opening a huge chasm at the rear. Internet sources say it is a 39x80 but my tape measure says 42x80. I’m going to buy a new mattress soon and will opt for the 42 but it will be a tight fit against the bunk ladder and might interfere with the fridge opening. Just wondering what size y’all have in yours. My 780 is a 2018 if that matters.