[GeoffR]

If you were using the `ePub fixed/adjustable top/bottom margins` patch in earlier firmware versions, it should be possible to compensate for the increased ePub header size in this version by changing the replacement value on the last line of the patch:

    # Replacement value: Set this to the size of the device's built-in top margin,
    # in pixels. This value is subtracted from the adjustable top/bottom margin
    # (if any) to compensate for any unremovable built-in top margin.
    # Suggested values are:
    #   0 For full-screen reading mode (fullScreenReading=true, all devices)
    #  15 for normal reading mode (with custom or disabled footer, all devices)
  - ReplaceInt: {Offset: 0x48BED6, Find: 1, Replace: 0}

In earlier firmware versions the header size was zero in full-screen mode and 15 in normal mode, same for all devices. For this firmware version, try changing the value in red from zero to the numer of pixels occupied by the new header.

I don't know the exact size of the new header/footer though, as I haven't installed this firmware version, and it might now be different for different devices.

This change won't reduce the size of the header, but it reduces the size of the top/bottom margins added by the patch by the size of the header, so that the total space at the top of the page should end up about the same size as the left/right margins except when the left/right margins are set smaller than the header. (But as always, this depends on there being no extra margins set in the book's stylesheets.)

Edit: Going by others' screenshots, a replacement value of 50 might be about right for the Forma.