I too have the corner bed and HATE it because !0 the mattress is lousy...we sink into the middle and have to "lift" ourselves out to turn over...thinking it's the memory foam? It's the "upgraded Serta" that came with our 2011 Sunseeker. Researching new mattresses as I write.
The other reason is the climbing over as you all mentioned. But, the bed making, I mastered!
First, you remove the mattress and staple fabric tabs all up and down the sides of the platform that you will be using later to tie the bedding on. I put 5 on each side and 4 at the head.
Next, Cover the mattress with a fitted sheet with elastic that runs from side to side to keep it in place. You only remove it once or twice a year to launder because you don't sleep on it...it's for "show"
Next,I created a sleep sack: I took a flat queen sheet, ( I used off white), lay it flat on the ground, place a nice double (I used a stipe) on top, leaving about7" of the flat queen all around. I believe I had to trim the double sheet to be small enough. Pin it all around and sew it on top of the queen. You sew the bottom and up each side but only go up about half way. ( so you can get in and out comfortably. Now sew tabs all around the queen sheet, to match up with the tabs you stapled to the platform. (that takes some measuring and was the toughest part of the whole job..lol) Now you lay it on the bed, tie the tabs together (bows are easier to untie for washing than knots.) pushing/pulling the sheet down snug around the mattress and you're ready to sleep. I'm not very good at directions and measuring for your particular RV may be different...I was really winging it when I made this but it works! Holds things in place which was my pet peeve. the top sheet lays a little better and keeps you "tucked in" with no bunching! If you want pictures or have questions, feel free to email me at claudiavanhook@gmail.com