BUT we must ask :: what is the point of such a knot,
an "adjustable" eye knot?! Unlike with some friction-gripping
*fixed* eye, where the eye size in indefinitely large,
these knots are tied with a maximum that can only
be diminished, tightened down --unless a long length
is left for enlarging. And tightening under load might
be problematic re stability/structure or just plain
limited by force & friction.
In my experience it is harder to make a very strong friction-gripping knot where the loop is adjustable by moving the gripping part along the standing part than it is to make a knot where the loop is adjustable via the working part.
Yes, tightening under load might be problematic, and untying, too.
One application of adjustable loops is to secure loads, but I think Trucker's hitch variations are more suitable for that in many cases.