Ok I did the experiment this afternoon. Twelve ounces of freshly harvested and freshly squeezed 'Rhode Red' Valencia juice, with two baseline readings prior, then following my numbers for about 2.5 hours, when the glucose numbers had come back down. It was less of a spike than I would have expected (I had not had orange juice in perhaps 10 years!), although there was a clear spike.
Whole fruits seem to have very little effect, in that the fiber and cellular structure slows down absorption much more than does expressed juice. Still, I'm pleased with these numbers.