Mno, we won't mess with stats. 1.2 was more or less the way we wanted in that respect.
I'll look into the scenes for vanguard & sentinel, and their Tship entries - if they really have turret models in the scene without a turret actually set statistically, won't be hard to fix. (Edit: Yup, you were right - turrets in scenes without definitions in tships.. I removed the turretmodels ).
To change it yourself, not that hard; you will need doubleshadow's 'X3Editor 2'. Via that, you will be able to open up the "Tships.txt" file from our mod, and change the speed entry to whatever you want for whatever ships you want . No coding or scripting involved, just scrolling a bit to find the ship called "Mamba Raider" and editing a number in "Speed" tab.