which 4 bags for the rear of my tandem?

[HotRodYJ]

I've read where guys thuink the RE8 bags are too much for the rear of a truck and make the ride too soft. On my tandem project, I will be running 2 bags on each rear axle. I was planning on RE7 bags back there but what is your opinion on runnign 4 RE7 bags? Wont that potentially have the same soft issue as the RE8 bags or maybe even worse? Should I run RE6 or even RE5 bags back there since there will be 4 of them?