Undercoverxp is customisable, you can create your own templates to suite your cases
Go to options
, then give it a name in the name box
on the left hand side you will see a box called size (applies to both positions)
enter the dimensions you need in them width
then above them you will see left position
and on the opposite side a right position
box tick automatic for both of them.
Go to the bottom tick auto detect
(uses this template without having to select it when it finds a file of the above size)
at the very bottom add line
add one for top tick dashed then left right and bottom remember to add them dashed.