This may be a ‘get a bigger hammer’ approach, but have you considered adding a sheet of 3/4″ plywood in the bed of your truck to raise the camper? Might be a simple low-tech fix and I doubt it would raise your center of gravity in any meaningful way.
More experienced truck camper gurus might have insight as to why this is a bad idea but it’s the first thing I’d try. Put it in, go for a trip and see if it works. If so, then I’d paint/treat the plywood to keep it from rot.
Curious to know what you end up doing.