Flowergirl, is your eight and one half feet the length of your space or the height of your space?

Betty Corning and Polish Spirit are two vigorous clematis in my garden. PS has been in place the longest and has 20 or so stems coming out of the ground. BC is a newer addition that everyone else says can get similar in size and vigor as PS. Prince Charles and Venosa Violacea are more moderate in growth with VV being not as vigorous in my garden as Prince Charles.

The 8 and a half ft is both ways, it's the side of my garden shed on the north. From what you say I will probably not put Betty Corning in that spot. I can find another place. Will that be too much shade for the others?

Shouldn't be too much shade at all. I have some clematis where they only get bright indirect light and they do fine. The further south in the US you go, the more shade the clematis can tolerate--in fact they appreciate it especially if the sun exposure is to the late hot afternoon sun.