Forgive me for asking something that may be obvious, and I mean no disrespect, but "Why"?
Is there a benefit to this on Figs? Normally grafting on apples, roses, grapes, peaches, is done to have a less hardy or sensitive plant on top, grafted to the rootstock of a very hardy or disease resistant cultivar. Or to dwarf the cultivar. The problem with this is I think if the top isn't hardy, It's just going to die back to the ground anyway and sprout up as the unintended variety.
I don't see a huge benefit. I would think you would have to constantly trim out the suckers. I would try it if I could see a reason. Fill me in.
Maybe: To obtain a hard to root variety.
Maybe: Get a headstart on a variety.
Maybe: Gain vigor?
Maybe: I answer my own question?