If its steep who cares, if its not you want all the speed you can get.
The price difference between extruded and sintered base is like $10 for a board and thats buying a small order for just 1 board. For a big manufacturer it would be about $3 I reckon.
There really is no excuse for using an extruded base on a powder board IMO.
Hovercraft is small for you IMO.