128 X 128 map problems

Since I am helping Mario Maniac and Mega Luigi on their next mod, they have ran into a serious problem with using 128 X 128 maps. Apparently their problems are exactly the same as one describes at DHW. Here is the thread to explain it a little more:

http://diehardwolfers.areyep.com/viewtopic.php?t=5856

There are responses on that thread, but it would be greatly appreciated if someone can look into greater detail what the problem (s) may be.

Thanks