1.  As a first step disable any anti-stretch option in the video settings and set it to "Stretch Ball with Table".

2.  Load a fullscreen table and change the backdrop values to Inclination: 10, FOV: 10, Layback: 35, X/Y/Z Scale to 1.0 and X/Y/Z Offset to 0.0

3.  Temporarily set the Min/Max Slope to 0.0 so you can place balls on the playfield

4.  Start the camera mode

5.  Start the debug mode (by pressing Q and select Debug window) and activate "Throw Balls in player" and place 1 ball on the upper half of the playfield, 
    1 ball on the middle and 1 ball near to the flippers. These balls should be your reference if you overdo some settings and become an egg or squashed.
	
6.  Now increase the inclination a bit but not too much I would say you won't need an inclination over 25

7.  Next increase FOV just a bit but again not too much. I guess you won't need a FOV which is over 30 but 45 should be the absolute limit

8.  Increase the layback. This one depends on the inclination you set in step 6. If you increase the inclination too much you won't need a high layback. 
    My highest layback angle was 51 but most of the time it's around 30-40.
	
9.  Next big step is the scaling. Try to scale both values about the same amount. This step highly depends on the table's aspect ratio. 
    Let's assume that a cabinet playfield screen is 16:9. The best aspect ratio for a table would be 16:9 or 1:1.7 of course. But if you
	recreate existing tables you won't have this ratio. The golden rule is to use an aspect ratio of around 1:2.0 if it's higher say 1:2.3 
	you have to scale the Y-axis too much to fill the screen and the whole table looks squashed (and the balls too ;) ) One good example 
	is Sharkey's Shootout. This table has a ratio of 1:2.3 and you shouldn't scale the Y-axis too much because there isn't much room for 
	scaling the X-axis. The only solution for those tables is to accept a border on the left/right side on the screen.
	
10. Last part is the offset adjustment. Normally you only need to move the X-axis a bit depending on the settings used in the other steps above

 

Verdict: The egg shaped ball comes from multiple facts: depending on the inclination, FOV, layback and scaling the perspective distortion produces this view. 
	     Especially FOV and layback are two critical settings here. There are tables out there which uses FOV of around 90° that is much too high. The FOV is 
		 the vertical FOV and the horizontal FOV is derived from it. A FOV of 90° or 50° means you would normally see more elements around the playfield but 
		 for a cabinet setup you don't want that. You will notice that a starting FOV of 10° will produce a quite good perspective view and it doesn't stretch 
		 the ball towards the playfield glass.

 

One other aspect to keep in mind: 

If you place elements around the table in the editor VP will calculate a different camera position then without these elements. 
VP calculates bounding boxes for each element in the editor and try to find the min/max values for X, Y and Z. 
Based on these min/max values and the backdrop settings the camera position is calculated. So my advice is not 
to place elements around the main playfield.