Justin,
I also have several Pakistan Mulberrys potted recently in 1 gallon root pouches. Sorry no scion, I rooted the pieces that were 1/2"-3/4" caliper and stuck those larger deep in the ground. These are actively growing not dormant, all are about 18". I took the cuttings in December immediately after it lost its leaves. I had no problem rooting them with bottom heat.
Like Desert Dancer said they are very susceptible to early frosts, but living near Houston your actually in a good zone for it.
The mother tree is trying to bud out now, and I cover it, and keep hoping these light freezes go away soon. I planted a 4 footer from Ison's last year in April, the tree grew several new un-branched trunks, two to over 10 feet and a smaller one which I airlayered, the original trunk never did anything. I barely water, so there they would probably grow even more, Houston gets a minimum of 20 inches more rain a year than we do.
It has beautiful, huge heart shaped leaves. I should have done summer pruning because I want a bush to pick berries from ground. I pruned both branches knee high and it is budding in multiple places and should be bushy this summer. From what I have read recently, I now recommend pruning twice a year to keep controlled.
Yours for shipping.