Couple of things. First, in your PROC SQL example, you do NOT need the CALCULATED keyword in this case. Just saying "HAVING sum_height>50" works fine. CALCULATED is used in situations where you want to reference a variable you created in the SELECT clause somewhere else in the same SELECT clause.
Also, in the PROC SQL step and in general in SQL, having variables in your SELECT that do not also appear in your GROUP BY and that are not being summarized (with a function like SUM, MEAN, MAX, etc.), is not usually what you want (sometimes, but not usually). For ex., here, you have name, weight, and height listed in your SELECT, but only name appears in the group by. I would just recommend that you think carefully about what you're trying to get with this result.
For the FEDSQL part, the way you have it (with regard to the HAVING clause) is correct - in general, "real" SQL does not allow you to reference a variable you derived in the SELECT clause in the HAVING clause. This is kind of a convenience feature built into PROC SQL, which is a much more forgiving form of SQL.
Hope that helps.