How do I combine UltraArc and CIUv2?

[KaktoR]

The first. Xtool will (pre)compress all files.

Note that xtool is not a final compressor. It just unpack game archives for better compression afterwards (in very most cases), so you will see that xtool in some cases double the output size.

I don't have the game but if xtool does nothing, means output size (data.arc) is the same as input size (pack folder).