If there is reverse plumbing as Sean suggested, that of course is a problem. I agree with Tom though, that putting 4 tanks all in series is not ideal for this setup. Having the 2 saddle tanks (in parallel) feed a Tee going to a 50 oz tank would help a bit. Then, this 50 oz tank feeds the next 50 oz, which then feeds the UAT.

But I have a dumb question: where are the inlets on your model??? I'm sure they're there somewhere! [8D]