for the installer to actually use the {app} folder rather then the {appdata}\.... folder add this to the setup.ini ( doesn't matter if it matches or not, just need to be there )
Code:
[ExtractSettings]
FreeArcFile1=Data1.cab;DestDir:{app};Disk:1;
FreeArcFile2=Data2.cab;DestDir:{app};Disk:1;
FreeArcFile3=Data3.cab;DestDir:{app};Disk:2;
FreeArcFile4=Data4.cab;DestDir:{app};Disk:2;
FreeArcFile5=Data5.cab;DestDir:{app};Disk:3;
FreeArcFile6=Data6.cab;DestDir:{app};Disk:3;
FreeArcFile7=Data7.cab;DestDir:{app};Disk:4;
FreeArcFile8=Data8.cab;DestDir:{app};Disk:4;
FreeArcFile9=Data9.cab;DestDir:{app};Disk:5;
FreeArcFile10=Data10.cab;DestDir:{app};Disk:5;
FreeArcFile11=Data11.cab;DestDir:{app};Disk:6;
FreeArcFile12=Data12.cab;DestDir:{app};Disk:6;
Tested on Wolfenstein - The New Order which is 9xdvd5 it used the {app} folder for merging the files.
This only applies for Ultraarc Versions.