Hello Ingo,
If all we need a 5 volt for RPI and other components, so why he used adjustable LM2956, I can see a benefit of adjustable in this DC/Dc supply:
http://www.amazon.com/LM2596-Converter-Module-Supply-1-23V-30V/dp/B008BHBEE0/ref=sr_1_1?ie=UTF8&qid=1443621986&sr=8-1&keywords=lm2596
which has the flexibility of output voltage, as far as fuse we could still have the same fuse on fixed 5 volt output!
P.S. I read the TI data sheet more than once