I just saw your other post with the rainbow image — I get it now. Setting panoff to true won’t look right. Instead what you want to do is duplicate your 16×16 side by side (32×16). Then give it a CONFIG.INI with MOVEX=1 and PANOFF=FALSE.
Just saw this thread and, even if nobody is around for the answer anymore, the secret is to create a 31×16 image. When you duplicate your image you need to cut the rightmost line (32) off because otherwise this is displayed twice. Then the scroll is smooth.