Great idea, Frank! Our local dahlia society is 90 minutes away so I don't go but I would if it were much closer.
I've never seen any dahlias that are over 4' at any store though they are sold online. The taller ones can be knocked over in a strong gust of wind and that's why we're supposed to keep them tied (several times) to the stake.
This one is 'Robert Too' and shown to be 4' tall with blooms from 2 to 3". In the collage you can see it barely reaches the top of the old post and rail fence, which was 3' tall. Quite often it's an experiment to grow them the first time. Then you get to keep records so you'll know better the next year.
This one is 'Peaches 'n Cream' (also sold as Peaches and Cream and Peaches 'n' Cream) and the packaging said it was 18" tall. Mine hit 6' tall so I'm glad I went with my gut instinct (after checking the plant database here and DG's site) and put them at the back, not in front!
