I know that when building a rock rig it is good to have a low center of gravity, but what about front to back? would it be an advantage to have the majority of wheight centered in the vehicle? How would it affect performance or safety to have it balanced more or less opposed to having most of the weight out front? The reason I ask, Im thinking of stretching my frame and front axle forward for wheelbase and to accept a slightly larger and heavier engine. Thanks in advance!

too much weight up front will make coming down a hill a little tricky. a friend of mine that has a Mog can tap the brakes coming down a steep hill and lift his rear tires off the ground... scary when it's unexpected....

too much weight towards the rear will make it want to do wheelies, not fun when climbing a hill..

100% yes,i'm always preaching that ...
on my samurai i stretched the front 24"(frame 6")
you will notice a huge difference in climbing a ledge,instead of mashing into the ledge ,the rig will effortlessly climb...

Put the weight in the center, as low as possible...man, I need to make YouTube video to demonstrate the principle of a hammer being pushed up a slope. Head on top and it wants to turn around...head on the bottom and the handle wants to flip...head in the middle and it is stable, heading up or down.

I personally like my my cog a tad forward,pretty much like stock only lower, but i spend more time going up then down(sorry...spent....need tires now)
My .02