It certainly could be done.
I have a seedling pecan down by the barn that I got up on a ladder and topworked the 4 or 5 main branches to a desirable variety about 10 ft above ground level. There’s no reason why I couldn’t have put more than one variety on. Still have a couple of lower branches that I need to graft over, as the nuts they’re producing are not as good as the grafted cultivar.
You’re probably never going to see a 2-in-1 pecan for sale, as it would almost certainly require a roostock with split trunk/co-dominant leaders that would be predisposed to included bark, splitting and premature failure of at least one side, at some point.
Ah I see, thank you! So a better option would be to graft one type onto a rootstock, let it develop, and later graft the other type onto several branches of the developed tree, rather than try to graft both at once in a split-trunk style?
Yes, but hopefully the variety you’ve chosen to build a scaffold network to graft onto has a reputation for wide, strong branch angles. Some, like Osage and Hark require close attention and training early on, as they’re predisposed to narrow branch angles and bark inclusion.