My hair transplant 8 month opinion? I'm not convinced about the first line where there are the singles units. (Photos)

A hair transplant is not about how many grafts you need but understanding your goals and expectations. 2000 grafts may be enough for some but may not be enough for you if your expectations are different. The results also depend on your hair color to skin color contrast, hair texture, hair style, etc.
If you are considering a second surgery it would be best to discuss your options with a doctor.  You need to explain to your doctor your goals and expectations. The doctor needs to examine you to give you a better assessment.

Based on photos, your hair looks great, especially for 8 months.  It may take hair up to 1 1/2 year for it to fully matriculate.  Patience is critical.  If there are concerns, discuss with your hair surgeon.  Best Dr. Anil Shah

It is usually more natural and masculinly attractive to not have full density in the first line of the hairline zone.

Actually result is very good .Do  not forget that we can never go near to the  native density of hair. Final result and canopy effect of hair transplant related with caliber of your native hair in donor area; characteristic of hair (waviness or straight hair) ; surface and density of donor area that directly affects the number of harvested grafts; color difference between hair and skin and finally hair style.  If you  are not satisfy with  result of your first operation, would better to check those parameters and think about to plan a second HT to increase the density .

The transplant looks great. The zone you are talking about is not as noticeable as it seems. You can always re-consult and dense it it up if you are not happy. As it stands it looks fine. 

From what I can see in your photos the result from one procedure looks good.  This would be a good time to see your surgeon to review results and discuss your concerns. 

It is very difficult to see the frontal zone of hair that you are discussing from these photos. You need to zoom in with a closer view to show this zone