Thomas,
The reason you are seeing only the second panel when you print both of them with EJECT_AFTER is because you are not setting ATTR_PRINT_AREA_HEIGHT, ATTR_PRINT_AREA_WIDTH, ATTR_XOFFSET, and ATTR_YOFFSET print attributes. By default, these are set such that each image will take up the entire size of the paper. If you need to fit multiple images in a single sheet of the paper, you will need to change these defaults. For example:
SetPrintAttribute (ATTR_EJECT_AFTER, 0);
SetPrintAttribute (ATTR_XOFFSET, VAL_CENTER_ON_PAPER);
SetPrintAttribute (ATTR_YOFFSET, 0);
SetPrintAttribute (ATTR_PRINT_AREA_HEIGHT, 1000); // units are mm/10
SetPrintAttribute (ATTR_PRINT_AREA_WIDTH, VAL_USE_ENTIRE_PAPER);
PrintPanel (PnlPrn1ID, "", 1, VAL_FULL_PANEL, 1);
SetPrintAttribute (ATTR_XOFFSET, VAL_CENTER_ON_PAPER);
SetPrintAttribute (ATTR_YOFFSET, 1100); // 1000 plus a 10 milimeter gap
SetPrintAttribute (ATTR_PRINT_AREA_HEIGHT, 1000);
SetPrintAttribute (ATTR_PRINT_AREA_WIDTH, VAL_USE_ENTIRE_PAPER);
PrintPanel (PnlPrn2ID, "", 1, VAL_FULL_PANEL, 0); // don't bring up the dialog a 2nd time
SetPrintAttribute (ATTR_EJECT_AFTER, 1);
Of course, you'd have to change these values based on your paper size and the panel sizes. It might take some experimentation to produce the best outcome.
Luis