Powering Arduino with USB 5v through 5V pin

I'm designing a simple PCB to interface a USB FTDI chip with some sensors, power, and an Arduino to control the sensors. I'm trying to keep connections/wires to a minimum as the system needs to withstand vibrations.

The FTDI cable plugs into a USB port on a PC and has a 5V supply line from the USB port. Is it acceptable to plug this into the 5V pin on the Arduino?

From googling I've read that the official stance doesn't recommend supplying the Arduino with a regulated 5V supply to the 5V pin, as it is not regulated like the USB connection is.

However, since I'm not using a custom regulated supply but the PC USB port itself, would this be safe?

Thanks.

the 5V is the output of a regulator, does not seems like a good idea

5v that you know is 5v is fine to put in the 5v pin. Prev poster is clueless.

from mega board schematic

2017-07-19 23_30_05-arduino-mega2560_R3-sch.pdf - [Arduino_MEGA_2560-Rev3.sch] - SumatraPDF.jpg|425x167

See reply #2