I am looking to pickup a full size mattress in my Scion Xb. What size mattress will fit in there? Any experiences?

Buy a tape measure to get the dimensions of your car and then ask a sales person or look online to get the dimensions of the bed you want.
Although l am not 100% sure, l think you will find the mattress will be a little too long for the Xb.

Just tie it to the outside (it will be a MAJOR improvement as far as looks)

That one sure wont fit inside.

There are ways to ''do it'' in a car without a mattress man.

haha. wow. someone wants to get some lovin in their little box! l dont think a full size mattress will fit, but you might be able to get a kids mattress, or even do an air mattress, that way you can fold it up when your not using it, but you will have it just incase. just take some measurements and then go to the store.

l moved a twin bed with the back open without a problem. So l assume thats about the limit, but if you wanted to just squeeze a matress, l guess you could squeeze a queen, but that is about the limit. Hope this helps.

-Ty