Description of color is wrong (see World of Iris website for
discussion), but you are probably right that it blooms at TB height in
good growing conditions. Blooms are more IB sized, and the stalks are
often IB height here. The blooming photo is from spring 2003. Light
yellow standards, lavender & yellow falls. All the stalks in the other
photo are from one sprawling clump, taken yesterday.

<Thanks for the pics, of your Autumn Twilight X Renown seedling, not bad
indeed considering that
'Autumn Twilight' is also quite old fashion, but it is not a IB, is it:

AUTUMN TWILIGHT (G. P. Brown, R. 1971) TB, 33" (84 cm), M & RE
S. brownish yellow; F. light yellow. Autumn Sunset X September Sparkler.
Brown's Everblooming Iris 1945.>

Linda Mann east TN USA zone 7