Yes, it is variable by only changing the roll acceleration as expected. Easiest way to test it is to drop the inertia and make the bank angle something that will be noticeable straight away (like 90 degrees for example, which means the ship will be able to go 45 degrees to either side). Too low values will make the FL physics engine freak out, so for simple no time test just change the inertia to like 1 and watch the ship go crazy upon any kind of turn.
