hey there catch'.
i think the "proper" way to measure is one that demonstrates effective, useable length. therefore, measuring from the balls really doesn't cut it...
try this: looking down on your hard cock, measure along the top, from where it intersects your body to the tip. don't press really hard against your body (i've heard this called "bone pressed"), just where the cock and abs intersect. the two measures wouldn't be that different anyway, unless you had a big belly. if your cock has a pronounced upward or downward curve, use a tape measure instead of a ruler.
for girth, measure around at the thickest part of the shaft. many are intrigued to know exactly where that is: base, middle, head, or equally distributed. if you don't have a tape measure, use a strip of paper to measure around, then put the paper next to the ruler to get the measurement. watch out for paper cuts!
have fun, and looking forward to seeing the results!