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I'm asking this because I'm trying to decide between installing BG1 Tweak Pack (I like the convenience tweaks such as unlimited stacking) but this is not compatible with easy tutu.

I don't know if EasyTutu adjusts item stacking in game.

Tutu is basically a total game conversion. It takes all of the game data from BG1, and uses the BG2 engine to run it. As such, there are some things that work perfectly with it, and some things that don't work at all.

This version of the tweak pack DOES work with Tutu, and has the increased stack sizes you're looking for.

The Gibberlings3 BG 2 tweak pack will work with the Tutu BG 1 [as it uses the BG 2 engine]. The tweak pack includes the increased stack sizes and is what I use on my Tutu install. In fact the tweak pack installer detects if you have Tutu and disables options that will not work in BG 1 [on the BG 2 engine] like companion options for companions not available.