Late Roman belt

[Medicus matt]

After all, you'd need two different belts, the one to wear over your armour and subarmalis being a few inches longer than the one you'd wear over a tunic?

Isn't that why belts have more than one hole? :?

With the wide, plated belt sets you don't have as much leeway.
Of course you can make the narrow strap that passes through the buckle as long as you like but you end up with a gap between the plates on the two wide ends, which I'm sure wasn't the idea.