Itll be fine but if you want some protection/piece of mind, use the switch and relay setup with the motor side on a fused supply and a suitably rated relay to take the current. Just bear in mind that you wont get much travel out of that switch so it might be better mounting it the opposite way up at the bottom of the tank, otherwise it may end up either intermittently cutting your supply out or just being useless. Also bear in mind that a tall tank with a relatively small plan view area (ie, like a 2l coke bottle but not a 2l coke bottle or it wont last long with methanol lol) will stop your fluid sloshing around as much, preventing the switch from being overactive.
