is my Donor Hair at the back inadequate for a 4,800 FUE graft? (photos)

4800 FUE grafts is a large case. For cases of this size we break the case up into two consecutive days.  From your photos it does look like the donor area could support this size case, but given your recipient photos I wonder if there is the need for that many grafts.

Based on these photos, it looks like 4800 grafts would considerably thin out your donor area. I estimate your frontal area needing a minimum of 2000 grafts, although this varies depending on the density you desire and design of your hairline.  Your density options will be limited by the finite nature of your donor supply. FUE harvesting would certainly limit you to a session of no more than and possibly less than 2000 grafts based on this photo you submitted. A proper physical exam, however, is necessary to determine exact graft numbers. I recommend following up with a hair transplant surgeon experienced in FUE surgery.