So, as far as I know, there are no 3-ups. The reason for 2-up and 4-ups was to allow the sculptor to sculpt the details on the figure. Then that 2-up would go into a pantagraph machine which would create a copy of the sculptor at half the size, which was 3 3/4 inches.
Sometimes when something fragile or highly detailed was needed, then Hasbro would create a 4-up.
YoJoe does have images of 2-ups in the collectables section under preproduction.
I have attached a picture of the version 2 Muskrat with a non-production color testshot of the figure for scale.