I use 2" ball when ever possible, I have also change 1 7/8 " couplers to 2" in the past, BUT I do realize the reason for the different ball sizes.
Most people think that with all of the different size balls it is easy to make the mistake like most of us has done buy putting a 2" on a 1 7/8" or a 2 5/16" on a 2"Which it does seem like all balls should be the same.
But each coupler size is put on each trailer for a very good reason.
For instance.
Like they put an 1 7/8" coupler on the harbor fraight 980lb. capacity trailer, & if you change it to a 2" coupler and say you sale your trailer (you know the trailers towing capacity) & the person overloads the trailer or puts to much waight on the tounge because the coupler ratings on the 2" coupler show a higher capacity, he gets on the road & looses control & hurts or kills somone.
Years ago we use to mass produce trailers & there are very strict rules reguarding matching coupler size to trailer capcity.
(Man I did'nt even mention the penal hitch)
I'm no diferent then 99% of you.
This may make more sence to some of you.
ALWAYS USE THE PROPERLY RATED HITCH BALL FOR YOUR TOWING SYSTEM.
Your towing system’s maximum weight rating is always equal to the lowest rated item in the system.
Your hitching system cannot be upgraded to a rating higher than the maximum rating of your hitch.
For example, a 3,500 lb. ball on a 2,000 lb. max trailer weight rated hitch does not increase your towing capacity to 3,500 lbs. Your hitching system is still rated at 2,000 lbs.
Conversely, a 2,000 lb. ball on a 3,500 lb. max trailer weight-rated hitch decreases your maximum towing capacity to 2,000 lbs.
The hitch ball diameter (A) must be the same diameter as the trailer coupler (1-7/8”, 2”, or 2-5/16”).
The shank diameter (B) of the hitch ball should be the same as the hole diameter in the (correct) ball mount you selected.
The shank length (C) should be long enough to allow at least two threads to be visible when the hitch ball is installed and the nut completely tightened.
Ken F.
P.S. So I guess the size of your balls does matter.
According to our big brother at D.O.T.
(Sorry I could'nt resist.)