Needing a new mattress for my LQ what is a good mattress without being too thick and taking up space?  I have average room in my gooseneck area and it fits a king.   So many choices out there, only want to have to put a mattress up there once. 

One that makes itself! OMG making up the bed in the nose of gooseneck should be an olympic event!

In my old LQ it came with a mattress but we switched to a full size Green Tea 8" memory foam pressure relief mattress.  I have a horrible hip that kills me without pressure relief.  I got it from Home Depot because they ship it vacuumed packed and it held up without a box spring.  The full size gave me room to crawl around and get to my storage on each side of the mattress.

I have moved to a smaller trailer and bought a twin air mattress with a 2" memory foam topper.  I can adjust the air in the mattress for pressure relief and when I am not using it I let the air out and roll up the memory foam topper.  I got both at Walmart.

My husband has a camper he stays in on the weekends. The original mattress was HORRIBLE! I purchased a Linenspa Memory foam with inner spring mattress from Amazon. We got the 10" size. We don't have a box spring at all. It has held up quite well! AND It's COMFORTABLE!!! It comes vacuum packed. They have multiple sizes. We have the queen RV (a few inches shorter than normal queen). I just looked and the queen/king sizes are $360-$388. This is the title of the product:

Linenspa 10 Inch Memory Foam and Innerspring Hybrid Medium Feel-Queen Mattress