Once you complete the channel setup and image in your sequence, go to the Profiles tab -> create profile from sequence. This will open the Edit a Profile window where you can change anything you wish. When your finished editing the profile hit DONE and it will ask you for a name. Type in a name hit OK and attach your sequence to the new profile. Use this profile for all your sequences using the same setup either by selecting the profile when you first create the new sequence or attaching the sequence to the new profile.
The profiles are located in the profiles directory under Vixen and I would recommend making a copy of your profile (and sequence) before making changes to either.
By the way the adjustable preview is located under the Output Plugins tab on the Edit Profile screen.
