I Had a Large Silicone Chin Implant Placed 4 Weeks Ago and I'm Unsure if It's Too Small? (photo)

The change in your chin projection before and after surgery is not dramatic and certainly is not in line with the ideal chin projection point as you have described. While a greater chin augmentation would be better, be aware that the forward projection of an XL chin implant vs a L chin implant is only a few millimeters which may still not get you to the ideal chin projection point. It would be important to look at the thickness of those two implants and be certain the difference is more than 2 millimeters. If not then changing the implant to an XL will still not be enough and you will have to consider another chin augmentation strategy. (e.g., stacking implants, wedge on back side)

Your question is very common and quite practical.  Just like many things in life it is hard to determine exactly ahead of time if an implant is "enough".  Part of this depends on the discussion you had with your surgeon.  Some patients just want a "slight enhancement" or "just something to help a little" while some other patients want a very robust enhancement.  Therefore, whether or not this is "too small" even after surgery is hard for us to determine due to the above.  In the office we can gauge the size of the implant needed using sizers that allow us to estimate ahead of time.  Whether the chin is augmented "enough" depends on your previous discussion with the surgeon, what you determined as far as the extent of the augmetnation and if you agreed ahead of time on what size would be best.  I would allow things to settle out and live with this for the next six months and if you are not pleased perhaps talk to the surgeon about a revision.  I would not make any rash decisions immediately post op.

In cases of male chin augmentation, a genioplasty can give a better result than an implant.  The genioplasty allows for a significant advancement without widening the lower face excessively.  Donald R. Nunn MD  Atlanta Plastic Surgeon.

Based on the after picture which looks like it was taken immediately sfter surgery, it looks like you could use a larger implant. However you need to be seen in person to have a proper opinion.