This breeching is a bit low, I would raise it one hole maybe two, you want the breeching about 4-5 inches below the point of the rump, less for minis.
The hip straps are in perfect position at the top of the croup, not always possible with all harnesses or horses, but it needs to be as close as possible.
The shafts are well behind the point of the shoulder, and when in draft as he is now the breeching is not loose or droopy behind. The breast collar looks good. The horse is not sloppy in the shafts at all.
The crupper looks loose, see how you can see a lot of daylight under the tail, but above the crupper, but, Arabs can be deceiving in this area because of their high tail carriage.
The saddle looks a bit too far forward, see how the top of the saddle is tilting backwards and the bottom is tilting forwards and it looks a bit up on the withers, but it also cold be the fact that the Arab has a round barrel, and it is put on that that way to avoid the boys belly.
Again I am being overly critical for informational purposes, if I saw this horse harnessed, which I did, I would not look twice at it, in regards to improper harnessing. Pilgrims photo is coming up soon, so I can critique his harnessing mistakes.