Hello again.. My report: It worked like a charm.
i only changed three lines in the installerscript.iss:
Compression=lzma/fast
DiskSliceSize=765000000
SlicesPerDisk=5
It took about an hour to compile, and 40 minutes to install.
The final sizes were:
DVD1: 3.68GB
DVD2: 3.56GB
DVD3: 3.56GB
DVD4: 3.67GB (With Support folder)
The reason i changed the lines was:
I compiled a first time and with that compression and that DiskSliceSize, the first DVD exceded the limit once you put de Setup.cab in it.
Then i changed the Compression just to make it a bit faster.
Thank you so much for the help
PS: Sorry for my (i assume) bad english :P