I think you can easily set -m0 compression across all cabs and cut the conversion time significantly.
I included the Bonus folder and ended up with 5.18GB in Disc1 (I'm not burning it on a disc anyway), but if my calculations are right you shouldn't go over a DVD5 without the Bonus folder which is around 980MB (the files from cabs 1, 2, 8 are 4.22GB uncompressed).
Bottom line is, give it a try without any compression, it's not worth it to save some disc space on each disc at the expense of a 4 hour conversion.
//Oh, I understand
For me space is not a problem, but time is