here is a rough drawing..

as you can see.. the black circle/squares represent openings on the tank.
i have a drain hole at the bottom of the tank but the problem is getting to that area requires me to remove my setup from the trunk..

what im thinking of doing is.. hooking up an air line to the drain so i can drain the tank via that line. Is it safe to connect an air tool line there?? to drain and to use an air impact gun when i need it?? thinking if i should make a tool set trunk..

 

Get 2 L brackets so you can rotate the tank 45 degrees to have atleast one port facing down.
I have the same type of tank but i have brackets to make it sit higher and tighter so it is flush to my parcel shelf so i am not wasting space in my trunk.
Also i mentioned i have an IR (ingersol rand) I think sears sells them.

 

heres my setup btw.

 

Like skperformance said, tilt the tank so you have that drain valve pointing down. Maybe you can add washers/spacer on one side of the mounting bracket to get those few degrees.

 

ok so i hopped in my trunk n tried to work on the tank.. its a real PITA so i decieded.. what if i remove one of the plugs n just syphon the water out?? would that work fine?