I doubt sonny is 16.1hh, I am about 5'9 and "T" the horse I use to ride was 16hh and her withers is about up to my eye line. So if your 5'2 and the withers are near your eye line then I highly doubt he is 16.1hh
where were they measuring? At the withers AND were they looking above the line or below it... also, how old was Sonny when you bought him? Qh's can grow heightwise for like 5-7 years and widthwise for up to 10 years... I know he's a registered paint I think is what you said but he looks like he has a lot of qh in him.