Use FlexAudio™ to create perfect loops. If you have a loop without a detected tempo, set the snap to measure aligned. Use FlexAudio™ to snap the sound to the nearest measure. Loop the sound first to make sure all loop points line up. Now it should be in perfect synchronization unless there are tempo changes during the loop, in which case, you should figure out the actual tempo of the sound.
Once FlexAudio™ helps you figure out how much to time stretch the sound by, you can set the tempo with a simple calculation. Just find the tempo of the closest tempo marker before the sound's start in this calculation. Tempo of sound = (Project Tempo) X (Sound's Time Stretch Percentage) / 100.0 . Switch the sound to "Adjust To Project Tempo" and then type in your new tempo.
If you have made a commercial and it needs to fit in exactly 30 or 60 seconds and you are over by a few seconds, just time stretch it with FlexAudio™. Have you ever heard one of those legal disclaimers? They are inhumanly fast and it is due to a sound being time stretched by about 75%. Turn off snapping and FlexAudio™ it to the desired length.
Time stretching can be set from 25% to 400%. However, in most cases, it will only sound good from around 75% to 125%