"Almost fine". I think I have to reduce ultrasonic range from 10cm. Will tell you more after making and testing final robot.
"Dpdt switch" I am just using those to switch "fwd/rev" on the motors and the sensors pair from front of robot to back ( as my four ir sensor are constantly on with vcc and gnd connection. However dpdt switches the input of Arduino pin 2 & 3 from front to back) same approach will be for two piece of ultrasonic sensor one in front one in back. Thanks