You are limited to (6) directly connected stabilized outputs when using the supplied cable loom for the input.
An extra directly connected stabilized output (total of 7) is available on port A when using a single serial input on port B.
As Bob stated above, up to (16) channels can be stabilized via a servo distribution box using the serial I/O connection.
Most Spektrum users connect via the cable loom. Some Spektrum receivers now output an industry standard SRXL serial output. This can be used as a single input (port B) which would open up port A for the 7th stabilized output. You could also source a servo distribution box that supports SRXL as an input.
Danny