Good question.
As you say the donor needs to be used wisely.
Your density, hair groupings, characteristics, surface area to cover will all play a major part in what can or can't be achieved.
One must appreciate that a shaved look stilll needs a lot of grafts as essentially the hair is too short to give any layering effect of one over another that most depend upon with a transplant in order to give the illusion of coverage, so, a good density and design is needed.
In my case, my loss was extensive, but as a positive I had very good donor density and planned from day 1 to some degree my surgery and design.
The frontal hairline needs good density as uses single haired grafts and then as you go back the density will drop and the bigger groupings are employed. The change will be subtle as especiallly with a shaved look there is nothing to hide, so everything is open and visible to the viewer.
The skill of the surgeon will really be a major factor in this along with the angles of the implanted grafts to give that covered look even when the hair is kept short.
I don't have 65 FU per cm2 all over my recipient area or I would have needed 14,000 grafts plus to treat the area, but, I do have a look that gives an illusion of density and pleasing to the eye as kindly commented on by Stingray and others who have seen me. I do have this density in areas but as said, a blend is then needed in order to get the required coverage and not overload an area.
If you can upload some pictures then I am sure the forum readers will be able to give you some good advice.