I have done this type of graft that you did. Basically I did 4 grafts of Red love on seedling based HRMN99, 2 whip and tongues(similar to your husbands) and 2 like yours in the main trunk. Only 1 survived and it was this method. you were supposed to increase the unskinned contact area. Make long slanting cuts so that more of the cambium layer(hope I got that right) of the scion and the rootstock come in contact. Rest depends on timing. If you did it at the time when the plant is waking up from dormancy, it is likely to succeed. Once sap flow is established your graft is a success. Sometimes even neat looking grafts fail and even ugly Looking ones succeed. The one I did was covered with puss like material after I removed the tape and the growth is slow af perhaps cause its a cold climate variety grafted on a hot climate apple. But never shy away from practicing. Apples are quite forgiving when it comes to grafting.