unorthodox approach
tap the adapter directly
Step 1
(you can do this with a script in bash) on machine 10,11,12
cvlc -vvv atsc://frequency=514000 :dvb-adapter=0 :dvb-srate=0 :dvb-modulation=8VSB --programs=6 --sout '#standard{access=http,mux=ts,dst=192.168.1.11:32000}'
do this on the three machines without tvheadend (or leave tvheadend installed and disable the adapter on the adapter page)
Step 2
then on the main machine make an IPTV mux in the running tvheadend with :
http://192.168.1.10:32000 as the address for the mux
http://192.168.1.11:32000
http://192.168.1.12:32000
do step 1 on the three "feeders" with different muxes make different channels on the main machine
not going to work if you have 120 muxes to move around but 2 or 3 will be nice and solid
Note the VLC command is for atsc so it will have to be adjusted for whichever your using
good luck clint