The BG2 Fixpack is an ongoing project to finally fix the last remaining bugs and errors left after numerous official patches and unofficial fixpacks in Baldur's Gate 2 and Throne of Bhaal.
Unlike the boots of speed, which uses haste or a 200% modifier, these just set the rate to 30 (description: double-strength haste). The bg2 default for pcs is 8 or 9*, so that would be 32 or 36. Easiest to just convert it to a 400% mod.
* I just measured the actual speed and like in bg1, both rates result in the same px/s speed, so I haven't been able to confirm the lore.
Unlike the boots of speed, which uses haste or a 200% modifier, these just set the rate to 30 (description: double-strength haste). The bg2 default for pcs is 8 or 9*, so that would be 32 or 36. Easiest to just convert it to a 400% mod.
* I just measured the actual speed and like in bg1, both rates result in the same px/s speed, so I haven't been able to confirm the lore.