Yes, the short answer is that grafting to a Gerardi does NOT dwarf the top. They keep shooting up at ~10’ per year.
The long answer:
I’ve also got a multi-graft “bush” mulberry which I’ve been trying to keep bushy through pruning. I gave up last year after it kept getting out of control.
So, last May I tried to graft a bunch of Gerardi scions to it, about 5-6’ up. Main problem was that I didn’t plan ahead, so I was harvesting partially leafed out scions and immediately grafting them. A few worked (very swollen bud was fine, but actual leaves was bad…), but it looks like I’ll have to re-graft some this year.
I’m not even sure this will be enough- it may be that grafting 6’ up is too high to start, as I’ll need to keep an eye out for any non-Gerardi waterspouts.