Ha! I did think about leaving them in pots, but everything seems to do better in the ground for me. I suck at container gardening.
What I'm thinking is, if I like the fruit of these and my seedling trees, I got lucky. If I don't, I'll have a solid base to topwork.
On a side note, I just tried my first mango tree graft (a Pickering cleft graft onto a not-so-vigorous PPK seedling).