We have an 2008 SV233T and I have often thought about doing the same thing. I did make an extension to cover the drop off at the edge of the bunk so that we don't roll off of our air mattress. Now that I'm retired I may revisit trying to find a solution, if so I'll post it.
Jim & Kathy
Bailey, waiting at the Rainbow Bridge
Gracie, a rescued Beagle
2007 Chevy Tahoe
2008 FR Surveyor 233T