Set custom paper size, always fail?

I've been looking for answer to this question many days but still, cannot set the paper size of my LQ2180 to 12'x 4'.

I tried more than 30 printer drivers but still no luck.

Is there any trick I can define a custom paper size in Windows or I am doing the thing wrong in Printer.width = 12 x 1440 and Printer.height = 4 x 1440 ?

'cos I have 10000pcs of continuous cheques to be printed so..

Pls help!
Many many thanks!