I think both exposures will work. True that the 5 hr. midday sun is an hour short of what's recommended, but it is midday sun! I haven't had success with bright shade.

As to growing taller ?? I think the nutrition of the soil is the most influential factor for maximum growth. The one I have in bright shade is tall but maybe it would be taller in sun? Don't know. It bloomed last year only because some rhizomes grew into a sun area. The other one there died out. My soil is heavy and I think it perished from poor conditions (lack of sun and heavy soil that didn't dry out enough between soakings). The one that lives is an aggressive grower.

I noticed a comment on why the first garden bed may have died, "may have been borers" I had a similar experience, when you say 'borers' is that because you saw drill holes in the shrivelled rhizomes. Mine did, and it was the black lawn beetle larvae, looks like a white witchetty grub or curled hairless caterpillar. Spent money on a granular killer, spread it on thick, for two seasons straight, reducing it down from over 100 the first year to 50 the next to none this year, And this year I've seen great new healthy growth and flowers.