The 16" Rossi only gained 100fps over the 8" X-frame and you still refute the statement that "I have found that the .454 Casull is one of the least barrel-length sensitive revolver cartridges available."???
Besides, comparing two different revolvers is nearly meaningless. In a world where any given 4" can shoot faster than a 6", I don't see the test results as anything we can actually use.