Yes, since you'll have to enter all the captures yourself anyway (either
with an @ preceding the position of the captured piece or a minus sign
following the position of the captured piece, say W b2-b4; b1-; W b4-c4;
a4- or L b2-b7; @-b3; @-b5. But if your rules differ too much from Ultima
as it is usually played here, perhaps you should modify the above preset
yourself with the Edit command and enter a slightly different name for the
game, such as Ultima with augmented Withdrawers, so that it gets listed
separately.