We have a similar sofa bed in our 27RLWS. The gap is the same, perhaps even larger, as I put a 2x6 behind the sofa to keep it from contacting the wall while travelling or during set up. The inflatable bed has been used numerous times, and when filled with air, is rigid enough so that it doesn't bend into the gap.
We always put the pillows at the wall end, and several different people have slept there with no one complaining.
Harv & Deb
2015 Flagstaff 27RLWS
2010 Ram 2500 4x4 crew 5.7 Hemi, 3.73
Equalizer 1200 4 pt. Tekonsha controller