1. When you say "loaded heavily", what do you mean ? Could you, please specify the load as a percentage of the MBS of the rope ? Is it close to 50% ( which is what I would call "heavy load" - if it is closer to 33 %, I would call it "moderate", and if it is closer to 25%, 'light" ).
2. I would nt call it a "double collar" (=two collars) loop. The one ( the first ) leg of the collar is "coiled", that is, it makes a helical turn, but there are no two U-turns, the one after the other ( a N-like collar ). And the two legs are not crossed, like it happens in the case of the " cross-gartered" bowline (1). In particular, in the genuine "double collar" bowlines, if you, accidentally, un-tuct the second collar, you are still left with the first, which still works - while in your loop shown here... well, you are still left with a helical turn, the simplest helical "knot", which you pray it will hold !
3. I am not sure that the total nipping force, delivered by the closed nipping turn tied on the Standing Part, and the open ( helical ) turn tiedon the returning / second leg of the eye, deliver more gripping / nipping power than a triple (=three nipping turns) bowline, as the Tresse coiled S.Part shown by Alpineer (2), or the even simpler Triple bowline shown by me (3)(4) - which have the additional advantage that their nipping structures are self locking. ( In fact, it looks like a transformation of those bowlines, where the one nipping turn of the "nipping structure", tied on the Standing Part has been replaced by one nipping turn of the "collar structure", tied on the returning / second eyeleg ).
4. I believe it is too complex - although easy to tie and untie. I do not see a clear "pattern" in tying it, or in its final form which would allow to inspect, memorize and remember it easily.
5. Having said that, it is clearly a new concept, where, although the loop is not based on a bend ( like the Tweedledee bowline - but there are many other, "simpler" bends not based on interlocked overhand or fig.8 knots, which can be turned into nice symmetric bowline-like loops ), nevertheless it utilizes the nipping action of both eyelegs.
1.
http://igkt.net/sm/index.php?topic=4283.msg35800#msg358002.
http://igkt.net/sm/index.php?topic=5357.msg36131#msg361313.
http://igkt.net/sm/index.php?topic=5357.msg36605#msg366054.
http://igkt.net/sm/index.php?topic=5418.msg36587#msg36587