Jackmanii is a type III clematis and should be cut back to within a couple inches of the ground every year or it will develop old thick wood that will eventually be devoid of leaves and all your flowers will be on the top of the plant since it blooms on new wood. The President is a type II clematis but in my zone 7a garden, I treat it as a type III clematis as well since my growing season is long enough that it just blooms later in the season than it would if I didn't prune it. I can even prune it back after its first flush of flowers and get another flush in the fall. In your zone 9 garden, you have an even longer growing season than I do so you can easily treat both of your clematis as type IIIs and whack them back severely and still get blooms. I think it is time to get the pruners out and give those plants a serious haircut. They should come back out within short order. I would treat them similarly each late winter/early spring.

Cut'em down!