I've tested the new Raspberry Pi 3 model B+ successful....

A project log for Raspberry Pi 3 cap rail enclosure

self made din rail enclosure with breadboard for Raspberry Pi A+ B+ 2B, 3B, 3B+

hwhardsofthwhardsoft 03/20/2018 at 08:440 Comments

We've tested successfully the new Raspberry Pi 3 Model B+ and our RasPiBox Open Plus din rail enclosure set. 

It fits perfectely in the enclosure set and the voltage regulator is strong enough to power the 3B+