On my commuter bike I am currently running a 700c wheel on a 26″ fork, since the wheel is bigger than the fork is designed for, I cannot use a standard v-brake. I have designed a v-brake with a slot so the brake will fit almost any wheel and fork combination.
I designed the brake using SolidWorks, which let me do stress analysis to ensure it is strong enough. I have accounted for a max force from the cable (average grip strength of a male) to be 450 N. I calculated the force necessary to stop a 200 lbs rider from 50kph to a complete stop in 10 seconds to be 260 N. Given those forces I have calculated a minimum factor of safety of 2.0 using 7075 aluminum.
After FEA was done, I 3D printed the brake arms to test fit everything. I wound my own springs using music wire and installed all the hardware. The brake works as expected for plastic, the next step is to machine it out of 7075 aluminum.