Quite a few of my micro fuselages can be made to fit the SR. There are people putting the SR inside of the Eflite UH-1 Huey but it was actually made for the Blade CP. Just checked out the SR dims and with a rotor dia of 552mm , its slightly bigger than the dia of the Blade CP and HBCP2 of 535mm. There really is no reason why the 300 size micro fuselages should not work.