you can try two things that come to mind.

1- set the 50hz speakers to large and use the protection circuit. this will give them full range sound and I am not so sure where the LFE goes as its been a while I've thought about this.

2- if your sub has a high/ low pass then place the sub somewhat close to one of the front speakers where it will have its best output and then run the L&R interconnects to the sub, run the high pass interconnects from the sub to your amp and use the xover in the sub. Then tell the G68 that your L&R are large with no protection and that you have no sub in your system. now you will get the full range sound + LFE to the fronts. You can set the rears (center?) as small and use the proper xover for them.

Have a look here:

http://www.meridianunplugged.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=1;t=000024

best regards,
Jerry

Best regards,
Jerry
Main System: 861v6, DSP8000s in corners, DSP7000s Center and Sides, 1-9 humans.