What is the intended PCB layout for this Lumberg stereo connector?
Looking at the datasheet for this jack, I suspect that this jack is intended for through-board mounting.  (Some manufacturers call it mid-mounting.)  The body of the connector goes into a cutout in the board.  The pins solder to he pads next to the edges of the cutout.  The pads may be either the top or the bottom of the PCB.  The advantage of through-board mounting is that it removes the PCB thickness from the overall height of the PCB assembly (if the jack is the tallest component).

What function do the plastic pegs serve in a through-board configuration?  They are an atavism from another variant in this connector family.  The manufacturer had reused the plastic injection mold which had the pegs.  

p.s.
The drawings for this jack are rather poor. If it were my project, I would be looking for a jack with a better datasheet.  Mechanical problems in PCB layout are hard to patch.  Why take a risk.

Here's a similar jack which shows through-board mounting in more detail: