It's a small detail that may go unnoticed but to make the seat and carrier look like a factory fit, the stamped grooves in the top surface needed to be addressed.
By ending them before they reach the saddle it will look like it was intended to be mounted together.
Again I started with the vinyl to protect the finished surfaces then filled the grooves with fiberglass filler.
Next it was roughly sanded flush.
After getting it close, the mask was removed.
I probably should've masked it farther back but all of the unmasked area is under the seat.