Change router address in Shibby 115

Hello everybody!
I have new Linksys E1500.
Before flash Shippy 114,I Set my computer IP Address manually to 192.168.8.1 and set netmask to 255.255.255.0
I flash "tomato-E1500-NVRAM64K-1.28.RT-N5x-MIPSR2-114-Max.bin" successfull.
But I want to change router address 192.168.1.1 to 192.168.8.1 in Shibby 114. I can't change it
Because my modem Vigor 120 address 192.168.1.1
Help me change it.
Thank a lot

p/s: My English is second language.It's bad
I can choose Shippy 114 or Shippy...

Change router address in Shibby 115