Thank you Dan Lehman, SS369,
Probably I should have presented the second variation of the "trefoil bend" along with the first, but, because their differences are so minute, I decided not to confuse the reader more than necessary. The main thing in my interest with this knot was the wide curves of the rope strands all over its nub, and, in this, the two variations do not differ much...( in fact, they are
almost - for all practical purposes - identical). Moreover, the "trefoil"/re-tucked overhand form I have used and shown, is the most "natural" that one is inclined to tie, I believe. It is produced by any careless re-tucking of (the/one) tail of a simple overhand knot through its central opening, without passing between the other end and the already shaped perimeter of the overhand knot. So, I have called this second form "trefoil X", meaning that the standing end and the tail are crossed before they exit the central opening. ( Of course, the first form is also an X / crossed form of the second, as well. But I believe that the first form is more "trefoil-looking" than the second

) ( See the first attached picture).
To tell the truth, I have tied both variations,
and I thought that the second one, the "trefoil X" bend was slightly better, as the standing end goes over the tail as it exits the knot s nub, so it secures it "more". But that is so secure a bend, its strands are so convoluted, embracing/twisting around each other so many times...I decided that "theoretical" "added" security was of no importance. So, I have to admit that I presented only the first variation for KISS and marketing purposes !
As of the relation/transformation of ABoK#525 to a figure 9 shape, I have not investigated how this could produce other bends. I think that, during that transformation, the most symmetrical form is the initial "trefoil X" one, and I have a soft spot on symmetry ! Moreover, it is unlikely that other bends will force the rope strands to follow that wide curves,
everywhere, all over the knot. I am sure one can tie many different bends if he interlocks some of those "transitional" knot forms, from #525 to figure 9. I have learnt about this transformation only recently, from a page of Charles Hamel s site, (1), from which I have copied and re-posted a picture here. (2) More pictures are shown at (3)( I thank SS369 for the information about this site and this wonderful man).
SS369, you have very strong arms and legs, to be able to distort the symmetrical round form of this bend!

May be you could have not achieved it if you have tightened it pulling the standing end/tail pairs
of each link/part, independently and in succession,
before you load the interlocked whole.
The "trefoil bend" is not sooo bulky, certainty less than the double Zeppelin. It is wide, but not fat !

The Double Zeppelin is perfect, almost as perfect as the Zeppelin, but one should not stay all his life with the first perfect woman he finds, should he ?

Your re-tucked true lovers / MWalker 2strands bend is also perfect, much more elegant than the double Zeppelin. ( It is one of the most beautiful knots I have seen ! ) If I have the time, or the experience to dress it correctly, I would tie this bend instead of the Double Zeppelin ! Its curves are a lot wider, so it is worth the added effort for a more "permanent" stiff ropes bend, I believe.
SS369, start a new thread about re-tucking common, old, known knots. There are much interesting things waiting for us there, I guess.
1.
http://charles.hamel.free.fr/knots-and-cordages/bats_belfry_5.html2.
http://charles.hamel.free.fr/knots-and-cordages/img/525-to-fig9-sum.jpg 3.
http://charles.hamel.free.fr/knots-and-cordages/PICASA_Slideshow/Du-525-au-Fig9/index.html