Thanks! I don't know if this was in Fx. 11's GUI out-of-the-box, but Session Manager does have a selection for this, and ticking it does change browser.sessionstore.restore_hidden_tabs value to true.
Not sure if these intermittent blank pages are related to this, as most tabs do load, and I will have to see what happens on Restarts v. Session Loads.
Either way, thanks again.
Aha, the joy of highly configurable applications, with highly configurable after market modifications.....