Shortening / Cutting Titles or Generators without retiming

I've created a project in Motion that I want to use as the background for B-roll footage in FCP. The longest amount of time that the B-roll is 4 minutes, but it may be much shorter. So I created a 4 minute Motion project with the first 8 seconds including some text that should fade out after 8 seconds and just leave the background for the remainder of the time.

Here's the problem. In FCP, if I shorten that background from 4 minutes to 2 minutes, it also shortens the amount of time the text is displayed from 8 seconds to 4 seconds. I'm trying to set up the project so that no matter how long or short I cut the Generator or Title (I've tried it as both), I want the text to always stay at 8 seconds long.

I've set the text up as a separate group in Motion, tried making it both a Title and a Generator (in case the behavior was different), but I cannot find anything in Motion or FCP to be able to shorten / cut the Title/Generator without also retiming the text.

Any suggestions or help would be very appreciated!