I'd say go for it. You will only be out the cost of the tuber if it doesn't work, and actually, you may be able to harvest some tubers from it for next year. And if it works, you totally win!

Some of my biggest dahlias are barely coming up and I may well have to do this with them...they were very slow germinators. Same thing happened last year with dahlias from this breeder but I got good tubers and were able to start them much earlier this year in my greenhouse.

I am only a few miles from you over the border in WI. I was gifted with a number of additional tubers late this year and just finished getting them in the ground last week. Last year some of my tubers didn't get in the ground till mid July. I still got blooms off of most of them, just not as many and not until September. All of them developed additional tubers, so I am able to see if they do better this year.

Since you have a green house and are growing them in containers, you can always move them inside when the early frosts hit. Seems a no brainer to me.