I believe with an FS with a fixed bed, lift struts certainly should work in your application. I suspect you may have to reinforce the areas where you locate the ball studs since there will be a lot of stress at those points. Doubtful the base was constructed to take the stress.
I really would like lift struts on my TS, but the way my mattress platform slides across the bed base because of the bedroom slide I have yet to figure out a way to make it work.
Good luck and post some pictures when you are done so others might try it too.
2014 Seneca 37TS
Toads: 2014 Ford Explorer Sport or 2013 Ford Focus ST