One final tip–you can actually use a crowfoot without calculating a new torque setting if you set it at a 90 degree angle. This is because the lever length is unchanged since the crowfoot is pointed tangent to the lever arm.
Ultimately, it is possible to torque these seemingly unreachable fasteners. With as little as a $10 crowfoot wrench set, an online calculator (you don’t even need to remember your trig!), and a ruler, you can save yourself the headache and hassle of a hole in your floor pan. You choose.