Greg,
Excellent sequence of pictures to explain how to set that FS...thanks for taking the time.
(and removed).
i think it is best to not have too tight a bight, to place less strain on the line at the bight. So, too small a small 'ring' would place more force on the bight. Also, smaller 'ring' should not be able to inset inside larger in use, for the same (t)reason.
Some, spoke previously of using this for lowering loads. This, can place more loading and impacting on that tight bight etc.; and change the mechanics from a closed system to an open one...
Caution too, that 'Friction Saver' is a misnomer, in that it still takes the same amount of friction, to provide the same amount of braking force(s). So, friction is saved at one point alright, but just to be reapportioned to anther point of system to provide the same friction/braking force- like moving the friction from the TIP to your friction hitch-that already is heating up from it's frictions it provides. So, now frictions and their heat is more concentrated, with no break in between (that 2 points of friction-TIP and hitch provide) to dissipate some buildup in heat before more friction/heat added. So, should go slower, and watch for more glazing of tail.
The accusations of flat rope/webbing are true here; but, on a non moving bight (like 'friction saver' sitting still on it's bight, carrying sliding load on it's own bight) flat is better (for the friction saver sitting still ,not the rope sliding thru), in that there is less 'height'/bent dimension to be leveraged at the bend around the support. In larger stuff this effect is negligible, but in smaller more exaggerated. So, maybe something inbetween webbing and round would be best for these occasions, like Tenex(?).