Oil change with apollo tank

[analog_me]

Hi,

Can you give me a hint on how to drain the oil from the apollo tank please?
following website suggest to use a 32 spanner to keep the tank in place so to apply enough torque on the allen plug nut to have it unscrewed.

http://alcester-racing-sevens.com/oil-change_pt__1...

My apollo tank doesnt have a 32 nut how do i undo the allen plug while preventing the apollo tank from turning with the nut?

Thanks