I don't.
However, you may want to check the actual capacity.
If you are depending on a tank monitor for level, they notoriously can get inaccurate with age. Especially the ones that use strip sensors outside the tank.
If the tank is actually over flowing in a time perceived as too soon for 17 gallons, it may be that it cannot be fully emptied due to a common design issue with outlet being at the bottom and not having a pickup tube. This will leave a couple gallons at the bottom and is normal. Or, the vent may not be at the top, further diminishing capacity.
An easy way to test it is to go to the pump out and empty the tank, then use a 1 gallon water jug and fill it with the hose while timing the duration to fill with a stop watch like on your phone or use your watch.
Then with the minutes/seconds per gallon rate noted, and the rate preserved because you didn't turn the water off, fill the tank at pump out deck fitting while timing it. Then do the math.
Or you could just count how many jugs it will take.
Just fill it till you hear that telltale increase in gurgle frequency, then you know the tank is full before spilling over or coming out the vent.