Hello @manny.hernandez,
It is possible to reduce the resolution of the orthomosaic (and only reprocess step 3 to get it). You could also add a processing area to your project so that only the zone of interest remains. This article should help: https://support.pix4d.com/hc/en-us/articles/202559989
There is also another community post on the subject, feel free to have a look there: https://community.pix4d.com/t/4413