I honestly believe that the supplies (logistics) system in AGEOD games is the most fascinating part of the simulation. Albeit a veteran of the game, I always find it amazing how even the most well planned campaigns can have a hard time achieving sufficiency in a foreign land, especially if the invasion is overseas and supplies need to come from the sea.
In all my PON games I have tweaked the supplies consumption to 2x to make it even more harder and unforgiving and I can confirm there are no major issues. I have some improvements to propose to make the whole logistics-marching story even more challenging and the expansion slower, especially in its earlier stages where the world is mostly made of dirt tracks and narrow unpaved roads. I am not sure if consumption is higher in underdeveloped areas of the map, but the development of a region should be slower to make early audacious campaigns harder.