Pam, just a side note, thanks for sharing that amazing piece of information about Frank Walter above. This is an absolutely great read about the history of the PW2800 and the way these engines were engineered.
I also admire your (and the other members) depth of knowledge and dedication to this project.
I think the P-61 will be one of the best aircraft to be had for FSX and will gladly donate an amount for it that is normally paid for a good payware product.
Keep it up!