I'm not surprised at the difficulty with pull-through sites. When you're backing up you can make big changes in trailer position over a relatively short distance with moderate steering adjustments, compared to going in forward and just having the trailer follow you. Also, most of us are accustomed to backing in, so we have that better worked out.
I use two spots in a row in parking lots (at the far end from the store of course), and I don't always hit the spot properly with the trailer position; it isn't trivial.
Originally Posted by Santiago
Why do you think Greg? longer distance to the tires? two axles track better when backing up ?
It's simply the longer distance from ball to trailer axles, which makes the trailer movement less sensitive to the angle at the hitch, or the position of the ball.
Tandem axles just cause scrubbing, which makes the path of the trailer a little less predictable - I don't find that it helps with backing up, and I wouldn't expect it to. Lots of people say they find a bigger tandem easier to back up than a smaller single-axle... but I'm sure it's the length making the difference. I've backed up our single-axle travel trailer and a tandem-axle cargo trailer of nearly the same size, and the travel trailer is easier to control.