Apple Engineering has reproduced this issue. It appears that the ImageWriter LQ GX driver starts printing about 3/4 inch from the top of the page. This occurs no matter which options (paper size, manual feed, and so on) are selected.
There are two possible workarounds if you wish to continue to use QuickDraw GX. Use one or the other of these:
If your application is QuickDraw GX-aware
You can use the GX Paper Type Editor (which is part of the custom install of QuickDraw GX Utilities) to lessen the added space at the top of the page by 1/4 inch. Follow these steps to create a custom paper type:
1. Create a custom paper type, modeling it after US Letter and giving it a top margin of 0 (zero) inches instead of the default 1/4 inch.
2. Save this paper type in the Extensions folder.
3. Use the Page Setup dialog box to select the custom paper type for the page being printed.
If your application is not QuickDraw GX-aware
Use QuickDraw GX Helper, which lets you disable QuickDraw GX desktop printers. So, you can use the non-GX ImageWriter LQ driver even with QuickDraw GX enabled. This method will provide the original margins.
QuickDraw GX Helper is not installed as part of the Easy install option of QuickDraw GX. You must use the Custom install option and specifically choose QuickDraw GX Utilities.