One of your fotos shows an apparant solid bar or strap supporting the
exhaust pipes. Solid mounted metal straps between the pipes and fuselage is
a NO NO.  Remember the motor is mounted on rubber shock mounts and it will
move up, down and sideways from Gyroscopic and powerplant vibrations.  You
are setting yourself up for exhaust pipe, exhaust flange or hardpoint mount
failure do to the restraint applied at the end of the exhaust pipes mounted
to the airframe. Not a happy event in the air.  The pipes should be
integrally supported by  the motor only and not supported at the ends onto
the airframe. Clamping the two pipes together near the end with the tips is
a good idea and offers triangular stabalization supportof the system yet
allows the system to flat with the motor.

Bob Smiley
N94RJ