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 the template from the kit doors. Remove the edge that represents the outer skin on 1 door. This will be the template for the for the inner thicker part of the gear door. Leave the other door as is to use to mark the outer skin of the gear door. Flipping the templates reverses the doors for both sides of the aircraft.
Make the inner door stiffeners. 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 is applied to prevent oxidizing and making the drink taste like metal.
Make the outer skin. As you did above for the inner part of the door, take the kit door the was not trimmed to mark the aluminum for the outer skin shape. 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 template 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. The 2 pieces together scale up to just a bout 1". Whether it is 100% correct or not I would bet it's a heck of a lot closer than 2 3/4". Regardless it is more visually appealing.
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.