I think your grafts will be fine- flagging tape is pretty strong, and was the first thing I learned to graft with.
As the others said, higher tends to work better. Personally I like to graft a little closer to the tree, and I like to place a chip behind the cleft graft to have a back up in case the cleft doesn’t take. Chip budding is quick and easy, and it only takes one bud; you can do it anytime the stock is active.
Here are a couple of links- the first is a little poorly done but useful, and the second a little better:
In the second one Hayes states that the timing is critical, but he is mistaken. Budding is typically (but not always) done in summer, but chipping is useful partly because it can be done in spring. I’ve done both. With chipping you do not need the bark to be slipping or even supple.
Mark is right, you can chip bud this time of year. I actually completed what I think will be my first successful chip bud a few weeks back. I added a chip bud on black gold cherry. It appears to have taken. My problem now is I didn’t think it through before placement and I don’t want to cut the branch off in order to push the bud. Stupid me…
It’s only stupid if you don’t learn from it. Otherwise it’s just that; another chance to try and learn. Chip buds still make me uneasy, but I should be doing them. I tend to enjoy T-Budding and feel I have better luck with it.
This tree is a little hard to get to with the current terrain and we really didn’t want to have a tall tree to spray so I wanted to make it a LOT smaller than originally. Just don’t want to kill the tree. It had so many branches in the lower three feet it made choosing the ones to graft onto hard.