Would like to know the reasoning behind filling the gear oil from the bottom. I am sure there is a reason, but I am unaware of it. I have a Suzuki DF150 and it has three holes in support of the gear oil; drain hole, air vent hole and oil level hole. Why doesn't this system work like normal oil, drain, replace drain plug, fill from above hole?
Another oddity is it seems that all of the oil drain plugs I have seen are to be removed with standard slot screw drivers. Seems like a poor design, but I could def be missing something.