Waterlogged ... were the distances between the Ys and Pumps (in and out) the same for both pump spans?

At the very least this should equally balance the workload and secondarily (I speculate) this should be the point that the least amount of flow back occurs during a pump failure scenario.

I am not sure how (if) this is applicable, but a home with dual hot water heaters deployed in parallel (same layout you are working with,) must be split so that work load (flow) is split equally so the total run length from split to split. http://www.plumbingzone.com/f7/dual-...110/#post37766

K-D