Limited memory - settings optimisation

I am working with a customer who currently has limited memory - 4gb to be  exact (patience argh!)

I took an extremely clunky model and reduced it from 20  mb to 2mb but now it keeps crashing (when it wasnt before)

do bidirectional relationships have an impact on memory, i know that's probably a silly questions as i am sure it does.

do you have any tips on how to improve the performance via the settings

1. Ive changed it to ignore privacy settings

2. Removed auto detect relationships 

is there anything else you think can assist here with optimising the memory?