Starting from this premise, I came up with the idea of two chains of fifths at 701.350 cents, spaced at 64.171 cents so that the tempered 9/8 (202.700 cents) plus this spacing yields a pure 7/6 (266.871 cents).
The spacing can represent either 28/27 (62.961 cents), as in the first lattice with D-E/|\ (9/8-7/6); or 27/26 (65.337 cents), as in the second lattice with E\|/-E (13/12-9/8). These JI thirdtone steps differ by 729/728 (2.376 cents). The spacing may also represent the complex ratio of 256/247 (61.959 cents), curiously smaller than 28/27 by 1729/1728 (1.002 cents), or almost exactly a cent, e.g. in the first lattice F-F/|\ (19/16-16/13); and in the second lattice, F#\|/-F# (39/32-24/19).
To find a counterpart to Scott's 19-note set, I have indicated on the lattice diagrams below a 10-note subset of the lower chain of fifths (Eb-F# in the first lattice, Eb\|/-F#\|/ in the second) and a 9-note subset of the upper chain (C/|\-G#/|\ and C-G# respectively) which together would yield such a 19-note subset.
This Sunvar-19 shading has close approximations for 19/16 and related ratios, while keeping ratios of 2-3-7 (e.g. 7/6, 9/7, 7/4) near-just, as well as some basic ratios of 13 (e.g. 13/9-13/12-13/8-39/32-117/64).
I should add that the original JI form of Scott's Sun-19 may be derived from two chains of pure 3:2 fifths (701.955 cents) at a pure 7:6 apart. He encourages all kinds of variations, just and tempered.
Lattice for Sunvar-24, 1/1 = D (on lower 12-note chain of fifths)
Subset used in Sunvar-19 after Scott Dakota's Sun-19
|----------------------------------------------------|
+1.9 +1.3 +0.6 -0.04 -0.6 -1.2 +0.6 just -0.6 -1.2 -1.8 -2.4
157.4 858.8 360.1 1061.5 562.8 64.2 765.5 266.9 968.2 469.6 1170.9 672.3
Eb/|\ Bb/|\ F/|\ C/|\ G/|\ D/|\ A/|\ E/|\ B/|\ F#/|\ C#/|\ G#/|\
128/117--64/39---16/13--24/13--18/13--27/26-14/9---7/6---7/4---21/16--63/32-189/128
/ / / / / / / / / /
/ / / / / / / / / /
/ / / / / / / / / /
19/18--19/12--19/16--16/9---4/3---1/1---3/2----9/8---32/19--24/19--36/19--27/19
Eb Bb F C G D A E B F# C# G#
93.3 794.6 296.0 997.3 498.7 0 701.3 202.7 904.0 405.4 1106.7 608.1
-0.4 +1.0 -1.6 +1.2 +0.6 -0.6 +1.2 +1.6 -1.0 +0.4 -0.3
|------------------------------------------------------------|
Subset used in Sunvar-19 after Scott Dakota's Sun-19
Horizontal lines = tempered 3:2 (703.711 cents)
Vertical lines = tempered 7:6 (264.844 cents)
Quadrangles from lower left = tempered 12:14:18:21
Two adjacent quadrangles = tempered 1-3-7-9 hexany
Generators of Sunvar-24 temperament: (2/1, 701.350, 64.171)
! sunvar24-19_16.scl
!
Variation on Scott Dakota's Sun 19 (24): optimized for 16:19:24 (2/1, 701.350, 64.171)
24
!
64.17091
93.25000
157.42091
202.70000
266.87091
295.95000
360.12091
405.40000
469.57091
498.65000
562.82091
608.10000
672.27091
701.35000
765.52091
794.60000
858.77091
904.05000
968.22091
997.30000
1061.47091
1106.75000
1170.92091
2/1
Lattice for Sunvar-24, 1/1 = D (on upper 12-note chain of fifths)
Subset used in Sunvar-19 after Scott Dakota's Sun-19
|------------------------------------------------------|
-0.4 +1.0 -1.6 +1.2 +0.6 -0.6 +1.2 +1.6 -1.0 +0.4 -0.3
93.3 794.6 296.0 997.3 498.7 0 701.3 202.7 904.0 405.4 1106.7 608.1
Eb Bb F C G D A E B F# C# G#
19/18--19/12--19/16--16/9----4/3----1/1---3/2---9/8---32/19--24/19--36/19--27/19
/ / / / / / / / / /
/ / / / / / / / / /
/ / / / / / / / / /
64/63--32/21---8/7---12/7---9/7--52/27--13/9---13/12--13/8---39/32--117/64--351/256
Eb\|/--Bb\|/--F\|/---C\|/--G\|/--D\|/---A\|/----E\|/--B\|/---F#\|/---C#\|/---G#\|/
29.1 730.4 231.8 933.1 434.5 1135.8 637.2 138.5 839.9 341.2 1042.6 543.9
+1.8 +1.2 +0.6 just -0.6 +1.2 +0.6 -0.04 -0.6 -1.3 -1.9 -2.5
|------------------------------------------------------------|
Subset used in Sunvar-19 after Scott Dakota's Sun-19
! sunvar24_dup.scl
!
Sunvar24, 1/1=D on upper chain of fifths
24
!
29.07909
93.25000
138.52909
202.70000
231.77909
295.95000
341.22909
405.40000
434.47909
498.65000
543.92909
608.10000
637.17909
701.35000
730.42909
794.60000
839.87909
904.05000
933.12909
997.30000
1042.57909
1106.75000
1135.82909
2/1