My 5'er bounces more than our last TT. Both about the same length. I've put shocks on both. The TT was solid, but the 5'er still has some bounce. The axle weight on each are close. The difference I believe is the stiffer springs on the 5'er. The TT had a GVW of 8400lbs, while the 5'er is 11,400+/-. The TT had about 2200lbs of CCC and the 5'er has 4315lbs of CCC. IIRC the loaded axle weight on the 5'er is around 7200lbs. Both ride on 225/75/15D tires. I think the bouncing is from the tires absorbing the bumps rather than the springs. Next set of tires will be E rated and run @80 psi.
Incidentally the 2011-12 FM like ours only has an 8400lb GVW with 1600+lbs of CCC. Same exact 5'er but with softer springs. I think Northwood my have dropped the ball on their spring selection. While it's great to have 2 tons of CCC, I think with the relatively light weight of the 5'er it and the stiff springs it's not a good marriage.
I've built a few utility trailers in my time and the ones that I put cheaper P rated tires on seem to bounce more than normal. I've thought about removing one leaf from each spring pack but it would be a guessing game as to what capacity they would then be.