There is a chance you will get a good pear, but a better chance it won't be good. I've had 3 or 4 come back from the rootstock, and most were little pears less than the size of a dime. Sometime later this month, I will be topworking those.
I did have one come back that was a good pear. My guess is that is was grafted to a seedling from a good pear, which had an offspring that was a decent pear but not exactly like the parent. The rootstock pear resembles a Kieffer but is earlier ripening and many hang until overripe and never drop. However, I am keeping this pear, because its a good eater and at a place I pass by frequently where I mow a trail.
I didn't know the rootstock on any of these. I bought them cheap and was willing to take a chance. All of them were supposed to be Kieffer, and so far the ones that lived have been what they were supposed to be.
I don't know what kind of pears that the common rootstocks in the OHxF series would produce, but I would like to know if anyone else knows.