I do not believe apricot makes a good rootstock, for itself or anything else. Al

Al,

Can you comment further on that? The OP suggestion surely wouldn't result in graft incompatibility.

Manchurian apricot is a common rootstock for apricot and I've not noticed any problems yet with mine.

Is there some root issue that would occur using a random seedling apricot rootstock?

Here is a link that might be useful: Apricot rootstocks

There are a number of reputable online nurseries that sell rootstocks.

There is nothing wrong with apricot seedling for rootstock, especially in Southern California where you need the vigor of a seedling to help widthstand drought and give you deep roots. Stay away from citation rootstock, a commonly used dwarfing rootstock. It's horribly poor for California because of it's low vigor and lack of drought tolerance.