BAMsE I'm sure that I've compressed files from original 1.0 version not 1.1 because I did it on my laptop not on the desktop computer that I play on. I've compressed both files (data1.cab and data2.cab) with the -mx -ld800 like you suggested but my files are:
data1.cab 1.5gb
data2.cab 3.0gb
I'm guessing that you hadn't left the sounds_eng.pck, sounds_eng_dlc_03.pck so your package for data2.cab is smaller.
Or there is something that you forgot to tell. Check your conversion
after recompressing the videos the profit is about 433mb so if you go lower with the recompression (the worst quality of the videos, believe me you don't wanna do it) you might even add the 1.01 patch.