Keep in mind that making an airfoiled stab doesn't always increase the weight of that structure enough to matter. And it often doesn't increase the weight enough that you could tell unless you had a decently accurate scale.

It's not like thicker stabs automatically make tail heavy models. Sometimes we're talking less than a ounce . Sometimes the weight increase in percentage isn't even over a couple percent. Using heavier covering can add more weight than going to a different structure does.

Sometimes it's not the difference, but the amount of difference.