Grasa, that is a work of art! I would be shocked if that graft does not take. From my limited experience, I know how hard it is to get the dimensions carved out just right. Congratulations.
Possible alternative to stem-root grafting??:
I have lots of healthy 1 gallon potted figs from last Fall's air layering extravaganza. I am using them for rootstock.
My one concern with grafting stem to stem is the risk of losing the grafted end to a late freeze (something that stem to root grafting would mitigate). However, if the stem to stem graft is done close to the soil level and the successful graft union is later buried below the soil, would that not resolve the problem? Or am I buying a new set of problems?
As much as I admire the stem-root grafting technique: to first bare-root a healthy plant for rooting material, then make the graft and then incubate the graft before replanting it, makes it a much longer process.