U-50 Firebox door

So far the only photo I have seen of the U-50 Franklin No. 8B Butterfly Firebox Door is the Baldwin builders photo #9808 on page 85 of Roger Polley's Volume 1. Unfortunately this is a quarter view and therefore I can not scale the door to come up with a size. I do have Franklin drawings for a model 8B which was used on the CB&QRR. When I place that drawing on the backhead of my boiler (20.88% of full size) it appears quite small.
Does anyone one know if Franklin Model 8B doors were all the same size, or were different sizes available.
Also, can anyone guide me to a straight on photo or drawing of the U-50 or 51 backhead?