I have runned for many years a T3VCS with a Spektrum HRS transmitter modul, and those SR3000HRS receivers have the old normal size case. With the Mugen MRX6 it just fits in the box but there is no space to wire a servocable to the other side of the receiver. Because the battery wire comes from the other side I had to make a slot at the side of the receiver case so the wire did fit.
Now with the T7XC and the 334SB receiver I have there is enough space. I think people whining for smaller receivers are known with the much more expensive Sanwa receivers.