The iron sights would be very easy, and with a scope, likely could see the stiching on Kennedy's collar.
Only problem, the front seat, the backs of the two front seaters, and the windshild and dash did not have Kenney's brains and blood spatter on them.
Instead, the spatter was to the left rear of the vehicle.
Don;t know about that, but the SS cleaned some of the inside of the limo as it sat at Parkland. That is curious, alright.