Theatermaster 8800 Speaker Configuration Question.

I could use some help with speaker configuration. I just upgraded from the EAD Ovation-8 (with Theatermaster 8000 pro software) to the EAD Theatermaster 8800 pro.

My room is configured as follows:

2 Martin Logan CLS IIz's with 2 Vandersteen 2WQ's up front

Martin Logan Theater Center Channel

2 Martin Logan Script surround speakers....directly left and right from the listening position

Radia LCR speaker in the rear center.

Velodyne HGS 15 for LFE

The 8000pro had a configuration setup for 5.1 with an speaker in rear center (called ES by EAD). Because there was no decent way to put two speakers on the L and R in the rear.....I opted for the 5.1 setup with a single center rear.

The 8800pro has a choice between a 5.1 configuration or a 7.1 configuration. There is no 6.1 or 5.1 + ES configuration.

I've been considering either running a classical 5.1 setup and forgetting the rear.....or alternatively, I could run the processor output for the L REAR and R REAR together to the single rear center speaker. Would this mess things up? Would it be preferable to have no rear at all? Are discrete sounds channeled to the L rear and R rear by the processor...or are they largely the same??

I'd appreciate any input.