One important factor in these temps is if its sunny or not. I don’t know exactly how much the wood (the graft junction in particular) heats up due to sun but a guess is 10 degrees, and it could be even more. So, 60’s and sunny could be as good as 70’s with no sun. I have been waiting for highs in the 70s or 80s for peaches but am going to change that this year to also include highs in the 60s and sunny. Also it doesn’t have to be a good temp every day, I’m not sure how many days you need but if there are two good days in the 4-day window after grafting that may be enough.
I can’t imagine doing that, it seems like the cuts would be too coarse and not at a great enough angle. But, its clearly working…