On a Windows machine, in the Printing Preferences dialog there is a box labeled "Paper Config."
Clicking on it brings up another menu with several settings, including "Paper Thickness" (in 0.1mm untis; default is "3", or 0.3mm),
and Platen Gap (choices are "Standard" and "Wide.")
I have no idea whether Imageprint even uses the standard Epson menu. If it doesn't, it should provide an alternative.
-Eric