I'm looking at a bike where I'll almost definitely change to a Thompson Elite post. The only length available in that diameter will be 330mm and long enough with about 35 mm to spare. Currently im on a seatpost with about 100mm extra. I'm a heavy guy and feel safer with more seatpost than the required minimum. Reasoning that there will be less stress on the frame.

Am I right in wanting more than the minimum insertion or am I concerned about nothing?

Edit: 35mm to spare. As in BEYOND the 63.5mm minimum.