There are actual dwarf retics that are not mixed. There are locale retics in different sizes.
If you want a dwarf, go for a pure blood locale. Like Jampae dwarf. Those are the medium sized ones you want.
The true super dwarf locale stay very small. About 6 ft.
The super dwarf x mainland creates a dwarf sized mix that can be anywhere from 10 to 15 ft depending on generation.
Look into breeders who have been dealing with them for a long time like The Retic Ranch.