Hi Sue, I just came across your post even though it is 4 years old! Cotoneaster does indeed make a dwarfing rootstock for pears and the pears I grafted to them are still going strong after several years. In Russia, there are pear trees grafted to Cotoneaster that are over 60 years old, so it is long term compatible. The only problem I have it my severe winter climate. Last winter I had -42C or about -44F as the low. So the pear varieties I graft to cotoneaster either died or took a real hit. But it works, it is long term compatible, and you get fruit. You MUST allow a few branches of cotoneaster under the graft to feed the roots, or the tree dies eventually as the pear is great at taking nutrition from the cotoneaster roots, but lousy at returning any. So graft a foot off the ground and allow a few shoots of cotoneaster (2-5) to grow in the first foot before the pear graft.