You're 1970-S is not a small date either. I struggle with measuring the height of these. I think the best indicator for a small date is the loop of the "9". In a large date, the tail of the loop is more blunt and points to the mint mark or the very bottom of the "7". In the small date, that same tail is sharper and points to midway up the "7". It is best to compare two 1970 cents side by side if you can.