"Hardly Even Recognize" (YOUR opinion needed)

I think "hardly recognizable" just suited what you meant. "Hardly Even Recognize" though looks like simple but seems more complicated. Just my take, English language is not my mother tongue.

I'd take the meaning you have given.

The only difference between "hardly recognise" ('even' is really redundant in the context you used - I'll explain why in a moment) and 'hardly recognisable' is that the first is a verb phrase and the second is an adjective phrase (both are modified by the adverb 'hardly'). The meanings of: "So long that you hardly recognize the person standing before you." and "So long that the person standing before you is hardly recognizable." are virtually identical and both imply that you had difficulty in recognising the person (but did do so, nevertheless). Why do I say that 'even' is redundant? Well, apart from its use as an adjective ("deep and crisp and even") and the rather archaic use as a time of day (as in "fast falls the eventide"), it is used as an emphatic to suggest 'going beyond what one would normally do or expect' - "I even showed him where the door was but he still didn't go!". "I even recognised the person" does suggest that there was some difficulty in doing so but it means something rather different from "I hardly recognised the person" and most people wouldn't express both simultaneously. So, by using the two adverbs together, it raises something of a conflict in meaning. I'm quite aware that "hardly even recognise" is what people often say but we often use redundancy in speech (our brains work quicker than our mouths and slower than our ears!) and quite often mix metaphors and misuse words when speaking. Of course, you wrote the sentence as you would have spoken it but some of your readers felt that there was a confusion in meaning, though they weren't aware of what it was, exactly, and therefore may have misinterpreted you.

Same thing. People from different countries may not have heard this before.

In my own perception, it tells something about how hard it is to understand. But your definition tells me it's okay.