I was wondering how big a human has to be in order to be called an Ogryn or how small to be a rartling?

I relaise that changes take place on planets with different gravity and conditions which over generations has brought about a change in build and appearance as well as to a degree inteligence.

However if a regular human family was posted to a planet that had these type of adaptations in the gene pool how long would it have to be before these attributes began to appear in the children of the new settlers. Say for example a regimental commander or a Commisar sent to oversee the induction of a new ogryn regiment, or even an Imperial Govenor.

Would children who had been second or third generations be considered to be ogryns, even if they were essentially human but maybe 7 or 8 feet tall? For that matter how about a particularly short ogryn of say just 6 or 7 feet, (If one had been fighting off world for a number of years and had a child born during campaign.) would they be looked upon as a a regular human even if they had ogryn level inteligence?

In short I guess the question is, how unhuman does an abhuman have to be before they are no longer considered human in the strictest sence?