Whip and Tongue Graft on Figs 

Whip and tongue grafts are commonly used in many species and I've found them to work well on figs as well.
Ideally, the scion and rootstock should be the same diameter. I will sometimes use this graft when the scion is down to about 80% of the dimater of the rootstock. This can be accomplished by cutting not as deep into the rootstock, carefully matching the width of the scion.