Oh TGC you don't know what you've just unlocked in me
so the new Dear Van Gogh trailer has this shot in it, which allows us to do something brilliant and convert Sky's world into real world units. Welcome to what happens when I get enabled.
According to Famousheights.net, (which admittedly does not cite its sources and thus I don't know how accurate it is but it's what I can find) Vincent Van Gogh was approximately 170cm tall. Using a non-angled image of 30cm ruler increments, we can measure his model up to that as our scale. Then, assuming the shown moff is of average height, we duplicate the image and move it over to the moff with ONLY the X-axis so we don't change our baseline.
Now, when I actually did this Ibispaint was a little annoying and didn't let me get the image to the exact size I needed, so yes, it is about a millimetre or two too high. However, that I fixed by moving the pink lines I drew for the moff and Van Gogh down a little, and either way, the size doesn't actually change since moving the lines also represents moving the scale down where I can't on the original image. Tl;dr, it looks a little too big when you look closely but it doesn't really matter as it's easily fixed.
To that end, the average height of a skychild appears to be around 109cm tall. Given the numbers I'd wager that this can probably be rounded to 110cm. Use this information however you like.
Boom. If anyone's already done this let me know lol.