a lot of people that use those will add a nail knot or two to make sure its on to stay.
I myself create my own loop by doubling the fly line back onto itself and then anchoring it down with tying thread and some flexible head cement. I start by anchoring the tying thread to create my loop size and then wrap away from the loop about 1/2", I will then add enough head cement so that my next set of wraps will get saturated through it, I wrap back to the loop then back up again, head cement again and then back towards the loop but only half way, toss in a 3 twist whip finish, make a few more wraps towards the loop and another whip finish then a few more wraps and a final whip finish (I usually do 2 on top of each other) then cut the thread free and allow the cement to FULLY DRY before doing anything with it. (after I cut free I will take my cement brush and smooth the head cement smooth with the thread to prevent hinging)
You can also cut away the fly line coating and do what I said or something similar to make your loop even thinner. I have never found the need though