7i92T with 7i77 and 7i76, modes 3 and 2 respectively

I'm trying to use all 4 low speed MPG inputs that I have, 2 on the 7i77 and 2 on the 7i76.  In my HAL file I have the line:

loadrt hm2_eth board_ip="10.10.10.10" config="mi,_encoders-=6 num _pwmgens=0 num_stepgens=0 sserial_port_0=3000xxx"
 
This loads and gives me the 2 expected MPG encoders on the 7i77. When I add "sserial_port_3=2xxxx" I get an error "num_sserials references 4 instances, but only 1 are available, not loading driver"

What am I doing wrong here?

loadrt hm2_eth board_ip="10.10.10.10" config="mi,_encoders-=6 num _pwmgens=0 num_stepgens=0 sserial_port_0=3002xxx

Exactly what I needed, thank you