Is there a reason you don't want to put in a booster pump on your RO/DI with a pressure cut off switch? That would be the best option if you can do it.
Something like this would work:
http://www.jlaquatics.com/phpstore/s..._ID=vt-rozbsts
or this:
http://www.bulkreefsupply.com/1-4-aq...-pump-kit.html