Be careful when you run weight and balance numbers with weight like that.
Maybe I'm wrong, but CG position for the seat is, I presume, the CG location if a person were sitting there. A considerable portion of a human's weight protrudes forward (calves, legs, feet, shoes etc.) and I would bet the arm of your load is further aft than the arm for a human load.
When I was testing my 8, I was using bottled water packages stacked up and started wondering about it, so starting with Van's cad drawing, I placed the cases and their corresponding arms into a spread sheet.
When I thought I was still a couple of inches forward of the rear CG max, I had extremely light longitudinal stick force, maybe even reversing a bit in the flare. After I ran the weight and balance with the real numbers I found I was right up against that aft limit, and pretty happy I didn't load a bit more in.
In the real world, with a bubba in the back seat, nothing in the rear storage compartment and right up to max gross weight, the airplane handles MUCH better than it did at the rear limit.
The rear seat arm for the RV-8 is 119.12.
4" different than my loading.