First up I apologise for my nonsensical post. Typing and thinking weren't connected!
15° might work sometimes but for me @ 189cm doing landscapes means a tall tripod with a head that allows me to (in portrait orientation) tilt the camera down a fair way to bring foreground (at the base of the tripod) into frame.
Also, if you were to use the levelling base in that way I think you'd be then needing to be more careful in levelling the tripod which then makes the use of the levelling base redundant.