cast resin smoke box doors

If I was to produce some smoke box doors, what would be a good common diameter? the cast would include the front of the boiler....Something like this.    

[Super]

Just about every face I have replaced with a smokebox door had different diameters. I like your design. Do you have access to molds and tools to make your own? Did you have to construct and form a lot for that fantastic ship you built?

Yes I would make the master,mould and cast them myself but it may not be practical if there are lots of different sizes.

[Super]

This is where I have been buying my doors. He has several different sizes. I start by using a caliper on the outside of the face I want to replace and I also measure the inside diameter as the doors also have an inside ridge which, when modified, helps to get the door centered when gluing. I then check all his doors to find one that comes close the these measurements. If you look at my Avatar, that smokebox door on Porter is about the smallest I have done.
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