Pix4D - Assistance needed

I uploaded my pictures to Pix4d from my drone. I got an excellent 3d map/model of the stock pile i wanted surveyed.
2 questions:
#1 When doing a volume i outlined the base of the stock pile, using the volume tool. I remember seeing a video of someone outlining the top of the their stock piles to come up with a volume. However when i try, i get a negative volume. Its only when i outline the base do i get something similar to what i figured it would be.
#2 If i want to improve the accuracy i can add ground Control Points. Do those points need to be visible in any photos? Or can they just be uploaded?

Pix4d is pretty user friendly, and they have a decent support site - put its all scripted answers.
Im hoping someone here has some experience with this program
Thanks!

a reply to: Macenroe82

Dont they have a forum?

a reply to: MrMasterMinder

Yup, i posted to their forum at the same time. Still no reply on there either.
But regardless, i figured it out over the weekend.
You do need to trace with polylines along the bottom of the pile - along the ground transition. That will give you an accurate volume.
And i found out you need at least 3 control points that are visible in the survey. You can manually enter them in the ray editor

The Control points are not mandatory, the software runs with out them. But if accuracy is mandatory, then you will need them