Picking a mattress has alot to do with personal preference and personal need. With two back surgeries, my mattress requirements are very important.
One trial run with the POS that comes with the camper told me NO WAY! I would have preferred a Sleep Number mattress like I have at home but unable to justify the price for the camper so settled on a higher end Beautyrest mattress. Did try the 2" memory foam topper over the factory 'mattress' that came with the Fun Finder but it didn't help at all.
The XT276 front bed is for a 'short queen' but the standard size queen mattress only overhangs a few inches so has worked out OK.
2012 Fun Finder XT 276 Toy Hauler & Harley Davidson Ultra Classic with Condor wheel chock
2014 Dodge Ram 2500 AT 4X4 Crew Cab 6.4 L Hemi, 373 gears, tow package, Rambox option, Revolver X2 tonneau cover, Equal-I-zer anti-sway hitch.