Multi Series movie can't forward over 2X

[coddon1]

I am trying to join a multi series movie from 2 DVD into 1. Each DVD have 2 episode in it. I rip all the VOB file from the DVD and use VOBEDIT to Join Clip them together. Then I used IFOEDIT to create the new IFO and use DVD2One to compress the movie into 1 DVD. Then I delete the IFO file of that the DVD2ONE create because it only show 6 chapter of 24. I then create new IFO with IFOEDIT again with default option. When I burn and watch them, I can fast forward to 8X on the first 2 episode. But when I try to fast forward more then 2X on episode 3 and 4, it skip chapter instead of fast forward. But if I just use 2X then I can watch the whole movie without any problem.
I was thinking of create 2 VTS file instead of one to help with the problem but I don't know how to make the VIDEO_TS file point to 2 VTS file on the NUMBER OF TITLE PLAY MAPS. IFOEDIT only create the VIDEO_TS to point to 1 Title only. Can anyone help me with the problem? Thanks