You don't need to worry about their roots being in shade if you've gone to the trouble of cutting a hole in your deck for that, I'm sorry it wasn't necessary.

They are vigorous type III Clems so they could grow six or more feet this year. I had some reach eight or nine feet their first year from gallon size pots.

They should be planted deeper in the ground than they are in the pot.

You will need to use supports to guide them where you want them to go.

They are Type IIIs that should be cut back to a couple of buds every year. If one is planted under your deck that could be difficult though you don't have to cut them back that far if you don't care about the flowers being at a lower level, they will send up new vines from the crown as they should which you'll have to guide.

Thanks buyorsell888 :)
Do you really mean that I can plant a Carmencita that is 3" tall in the dark under my deck and it will still grow!!?
Also, a question that I forgot to ask...is there a problem with planting them within a foot of my house foundation?
Julie

No, I don't mean that you can plant it in the dark under your deck and it will still grow. I meant that you don't need to plant it under your deck to keep the roots cool.

gotcha...I made the hole in the deck for practical and aesthetic reasons, thinking that the shade would be a good environment for the clematis roots. I will put it into a slighty larger pot and wait until it puts on some height before planting.
Thank you for your advice
Julie