Very supportive and extremely comfortable!
There is a nice, tight fit and it certainly does add some support for a heavier load. The shape works best with the belt. It is a must if you wish to use is without the F1 mainframe and can be left in even when the pack is attached to the frame.
Is it compatible with the little big top? Would I need to remove the plastic frame sheet or leave it installed?
Fits great and does exactly what it is supposed to.
The Endo G-type internal frame really improves the performance and comfort of my Transformer pack as a stand alone ruck for early season scouting.
Definitely a must have if you plan to use the Transformer without the F1 Mainframe.