Hitch height for 2720SL

I am setting up my 2005 just purchased 2720SL. I don't have anywhere flat enough to get an accurate measurement of the height of the hitch. I need it to set up my trailer ball height on my equalizer.

I am going to pull with a 2006 diesel Jeep Liberty. Brought it home with no WDH and really think its a great idea.

Is there any harm in drilling the holes for the sway control ball on the trailer frame?