Quarabs I believe are recognized by the Arabian horse association. I know that they have classes specifically for Registered Half-Arabs. I am sure that there are specific crosses that are acceptable.
I think the OP is asking more about conformation, as in for discipline. As someone said, there are MANY sizes and shapes of QH's.
Reiners and speed eventers are short and compact and look more like the foundation QH's, there are ranch horses that have a different look, cutters and ropers have a different look, so do english and western pleasure. If you ever go to a QH barn you can pretty much geuss the horses discipline by it's size and shape. What might be fun is to do a QH thread where people post their horse and explain the disciple. It would be pretty intersting to see all the different looks...
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