Most, or atleast mine(I have a 1987 19' Ski Eliminator in addition to my 2007 19SS Crownline) have a flat bottom for Solemn Sking. At at around 27-30 miles an hour the wake disapears and it is flat as can be behind the boat. The balasts or extra weight is put there to make the wake bigger when at wake board speeds but are not usually used for sking. These boats also have fins that protrude from the keel about 6" allowing them to cut and turn really well (they don't slide!!). A downside to pure inboards is they do not handle underwater obstuctions or shallow well at all as the prop is held by a non-moveable strut under the boat. Engine alignment is essential for them to work properly and the room for error is little. They do get allot more horse power and torque into the water. On the Ski Eliminator are not any gear reductions so if the engine turns 4500 RPM the prop turns the same speed.
There are pluses and minus to both, it all depends on what you want. My Crownline rides like a caddy and the Ski Eliminator is very ruff and unforgiving. They both have their place and are both very good boats for their intended uses.
2007 19SS w/4.3L Carb 1.87 Alpha 1