Basic Interstem questions
If you have say Magness pear on quince. And you graft say a quince compatible cultivar (QCC) on the Magness...
1. Will the new QCC have zero added, some added, or full added precociousness (i.e. take advantage of the quince rootstock?)
2. If you graft a quince INcompatible cultivar on the Magness--will the graft fail because eventually it leads up to quince rootstock?
My vote (based on nothing) is question 1: some added precociousness, question 2: graft will succeed!