Drain the tanks? Then you have a bare metal tank which to me isn't that good an idea. Also not kind on cork washers in fuel taps as I found out to my cost when they shrunk beyond repair and needed replacement.
Stabiliser? I find it hard to believe that a 1-2% mix of anything will fix all of the ills of modern fuel and prevent corrosion due to water content.
Fill the tank to the top? Hmmm. Even more fuel and more water hygroscopically absorbed by the ethanol.
Luckily I have discovered a better answer. Aspen is a pure petrol sold in 5 litre containers designed primarily for use in garden machinery. Putting aside the fact that it is way more environmentally friendly, it has NO ethanol and is so pure and stable that it lasts for five years before loosing any potency. The downside is cost, but at around £18 for a once yearly five litre slosh, its a damn sight cheaper than a new tank or an ultrasonic carb clean. Aspen is available in straight petrol or 50:1 premix. Get the blue can and if you need to put 2 stroke in it, you can mix your own ratio.
I've just drained all the rubbish out of my tanks and installed a can of Aspen in each bike and flushed it through to the carbs. No more sleepless nights, and as a bonus, you end up with a very nice re-useable container to store pump petrol for the car or mower.
Here is a link to the Aspen website: