Stupid tip for gastank rust <flakey>

I keep getting brown bits in my fuel filter. Getting a new tank, but have been reading archived posts about POR-15 etc. Until it's done, I'm not throwing my lug wrench, etc. in the trunk...I guess that every time I whack the fuel tank I might be knocking rust off inside...also keeping it almost full ($1.82 per gallon Atlanta)!!! a VENTED aftermarket cap is a MUST - I ripped out all that dash venting crap ('72 Super)and plugged and taped the lines....I still get fumes (when overfilled), so going to look at ways to seal the hole where the cable comes through from the latch door...