SMT Designs is Steve Thatcher's company developing products for rocketry, electronics and low cost professional prints. Steve has been a science nerd his whole life and taking photos most of that time. Steve's work career was as an electrical engineer and he did a wide variety of projects in embedded systems, hardware design, and software applications. Steve is retired from that day job and now devotes his time to his own engineering pursuits and photography which he thoroughly enjoys.
Of course this site is all about rockets... The mainstream product line is a series of 3D printed parts for creating electronic bays for rockets from 38mm, 54mm and up. The products consist of modular parts that can be attached together to create an electronics bay. There are also complete kit of parts for the more popular sizes.
They handle custom, single, dual, and redundant deployment (L3) designs. They also allow for re-configuration, re-use, and even easier field upgrades. Two great places to start would be Electronics Bay Design - Putting It All Together and Diagrams, How To's & Concepts. Of note, there are several products that can be used in more traditional electronic bay designs and they can be found in General Rocket Components.
Also, if you have specific requirements and you don't see exactly what you need here, contact Steve and he'll talk about solutions for your project.