It is true to shoot a 2 3/4 paper shells instead of a 2 1/2 paper shells build up extra pressure. But if someone shoot 2 3/4 plastic shells, it is much thinner than paper and it does not build up as much pressure as paper shells. It is why some have been shooting plastic 2 3/4 without noticeable kicking.
But light load should be used. In the old day, the 65 mm was around 6000 6500 psi, the modern 2 3/4 are about 11000 13000. That is enough to ruin some old guns. It is close to the proof load too.

g gournet