Unable to get the "remix duration" to 5 seconds

Hi, 

I have a handful of 5-second graphic logos I'm trying to remix music to. But for some unknown reason when I use the remix feature and drag the audio clip to match the 5-second video graphic, it won't stay there, it just extends out to about 13 seconds. I tried changing the duration field in the Remix properties > essentail sounds panel to 5 seconds, but it won't stay at that duration. Next to the duration field it says (+/-5 Seconds) but it won't see to go down to 5 seconds. 

To summarize, I am unable to get the remix duration to 5 seconds, which is what I need for this project. 

Any suggestions or ideas on how to fix this?

Thank you, kindly

P.S. While I'm here, if you happen to have any tips for speeing up the renduring process of mogrt files for playback and/or export, would appreciate any insight you'd be kind enough to share.