if there is weld marks all around the beam its been cut. to me the easiest route would be to get a new used beam and start from scratch. they seem cheap on the samba.
if its not ben cut, then just stand in the front or the middle and keep all limbs away from the trailing arms, and loosen everything. i cant see anything too dangerous happening if you stay clear. but just in case have a phone handy to call 911
ill check mine tonite to see if there is a set scew you might have missed.
i dont have that setup, but have done several hours on how they work, i like to completely understand something before i try it.
ok just looked on the stf and you do need to totally loosen the center grub bolt, should be done with a hex wrench.
let us know what happens.
neil