The OEM filter on a 6.0 truck at least caught all the bullshit from the delaminating tank, and just caused a fuel starvation issue once clogged. Happened on the road one time, which was frustrating, but that was a filter change away from being fixed. Had I known then what I know now, I would have changed the tank out then and there, but the fuel starvation issue happened a second time a year later, same silvery garbage in the filter, and I made the connection.
Point is, adding a second filter is a good idea, but when the tank starts delaminating, there's SO MUCH garbage being sucked up the pickup that any filter will clog, given enough time. If your tank delaminates, it needs to be changed, regardless of the filters you have.
Titan tanks are expensive, but guaran-damn-tees that the delam problem, or rust, will never ever happen.
I think I have some pics of the fuel filters I took out when my tank was delaminating. If you have some pics of yours, we can compare to see if that's your cause of the pressure drop.