Hi,
Please understand one thing: no amount of fiddling in the Form will change anything if the SAP device type used for printing sets the line spacing to 6 LPI... Which is what, for example, the device types EPESCP and EPESCP2 for line printers do for Page Format LEGAL (and actually all Page Formats):
Now, EPSON LQ2190 specification says: Line Spacings 1/6" or programmable by 1/360" are supported. You'll have to program the non 1/6" LPI in the SAP device type, however - probably via custom Page Format or something. What you will do in Form will merely adjust the SAP print preview to the physical output controlled by device type...
You can continue the fruitless experimentation in the Form, or you can find out an answer to a very basic question already asked 5 days ago: what SAP device type is used for printing? 
cheers
Jānis