Landing gear doors are usually an item that can be out of scale. The general configuration is an outer skin and some sort of stiffening structure. By the time the part is molded in a size the will not break to easily, it can be very thick. The Spitfire door used in the example below scales up to about 2 3/4" thick. Using the kit parts as a pattern, new thin doors can be easily replicated.
First, make 2 pattern from the kit doors. Remove the edge that represents the outer skin on one door. This makes 2 patterns, 1 for the outer skin and the other for the interior stiffener. Flipping the patterns will make the doors for both side of the aircraft.
With a sharp scribing tool, trace the outline of the inner part of the door on a piece of .015 sheet styrene. Rub over the outline with a pencil and rub that away with your finger. That will fill the "scratches" for your cut out line.
Nothing makes a better metal skin than metal. Aluminum from a soda can is great for making this type of part. It is very thin, fairly stiff, will hold its shape went bent and cuts easily with small scissors. Cut a small piece and wet sand both side to remove the coating that are applied to prevent oxidizing and making the drink taste like metal.
I know I will be accused of getting lazy in my old age but please just read the note directly above.
After all the parts are cut out, hold them together with the pattern and make final adjustments to the shape as needed.
Glue the inner and outer pieces together and give it a slight curve to match the bottom of the wing. This scaled up to just a bout 1". I don't know if that is 100% correct but I would bet it's a heck of a lot closer than 2 3/4".
Here is the finished landing gear with some photo etched parts and brake line made from thin solder. Tape is used to make the bands for the brakes lines.
