I aso did something like this to atipical overlay size:
&overlay FOREST LOOP create
&overlay FOREST LOOP shifts to 0 243 in zone 1 in 0
&overlay FOREST LOOP scales to 1.253 1.253 in 0
&overlay FOREST LOOP moves to layer 1
&overlay FOREST LOOP opacity 1 in 0
&overlay FOREST LOOP_2 create from FOREST LOOP
&overlay FOREST LOOP_2 shifts to 903 243 in zone 1 in 0
&overlay FOREST LOOP_2 scales to 1.253 1.253 in 0
&overlay FOREST LOOP_2 moves to layer 0
&overlay FOREST LOOP_2 opacity 1 in 0
&overlay FOREST LOOP_2 shifts to 0 243 in zone 1 in 2 THEN overlay FOREST LOOP_2 shifts to 903 243 in zone 1 in 0 loop INFINITE times
&overlay FOREST LOOP shifts to -903 243 in zone 1 in 2 THEN overlay FOREST LOOP shifts to 0 243 in zone 1 in 0 loop INFINITE times
This is my script but it will not work for you because you have for sure different size of the overlay…you simply have to find she right lenght distance between the overlays to make it smooth…mine was as you see 903 pixels…