You didn't state the host that you're using, but for this solution I'll explain how to do it in Adobe After Effects.
Start by creating a new composition that is the length of the retimed piece, which in this case is 4:24 and add the original clip to this composition. Then you'll need to make a precomp of this composition, which creates a clip with a total length of 4:24 - the video will remain 3:24 in duration and the frames in this new clip from 3:25 on will be blank. Next, apply the Optical Flow filter to the precomp. Now when you set the Optical Flow speed to 70 percent, the filter will have room to expand the video and you'll be able to see the full retimed clip.