Well, if I'm not mistaken, Cal's are hybrids between kumquats and tangerines (?not sure on the tangerine part). And I don't think Cals need that long to fruit, I think it's more of a size issue than an age thing. All this to say, if cals get their fruiting properties from the kumquat side, I'd bet it would flower when it's a foot or more.
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♣Gen