Less gas, but more wing left if hit by anything larger than BB!
The only effect foam has on the maneuverability of the airplane is that it takes up 3% of the fuel tanks' capacity. No added weight/CG effects. Haven't missed that displaced fuel in 15 years of flying USAF Alberts, especially not in a Herk with aerial refueling capability.
Haven't worried about missing 23 feet of wing either flying into places like Angola, Bosnia, and Iraq.
Keep up the good work.
ExHerkmate