I’ve already done so- at least 3-4 sucker transplants from my So. I’m not sure if they are rootstocks, or if the So is on it’s own roots, as some from JFaE are. Here’s a pic of one. There are two (apparently live) grafts on it: Bok Jo from last year and Dae Sol Jo Dae Chu from this spring.
Here’s a pic of my fastest growing Dae Sol Jo Dae Chu graft. It’s on top of GA 866, which is right next to the driveway (blacktop providing more heat) and with almost dawn to dusk sun (hard to do in developed areas).