Challenging scenario. I think rear wall is vital to imaging
and bass support etc but,… how to omit side wall reflection?
perhaps sound dampening? With both side walls you’re still dealing
with unequal reflection timing, so how do you address that? And
you wont have the imaging that you would with rear reflection.
challenging scenario. You didn’t mention speaker separation
distance or whether you will treat it as near field listening.
good luck and all the best.