ok now it completely ignores the cabs and install blanks :-/
records ini (data3a+b are manually created 7zip files not splits)
Code:
[Record1]
Type=7-Zip_Original
Source={src}\Data1.cab
Output={app}
Disk=1
[Record2]
Type=7-Zip_Original
Source={src}\Data2.cab
Output={app}
Disk=1
[Record3]
Type=7-Zip_Original
Source={src}\Data3a.cab
Output={app}
Disk=1
[Record4]
Type=7-Zip_Original
Source={src}\Data3b.cab
Output={app}
Disk=2
[Record5]
Type=7-Zip_Original
Source={src}\Data4.cab
Output={app}
Disk=2
[Record6]
Type=7-Zip_Original
Source={src}\Data5.cab
Output={app}
Disk=2