90 degree backing...

I can tell you from experience That the easiest place to have your tandems and still make tight back ins is at the 41' mark.

If you slide it further than that and you aim your tires too close to sight side pole or truck you need to cut around you risk hitting things with your overhang.

Especially if you are attempting this were the ground is not level. I some times make a visual mark on the ground were I need my sight side trailer tire to be and aim there trying to get the right angle as well.

The biggest key is aim your tire not the end of your trailer!

Rookies tend to aim the rear and as they start cutting in, the over hang swings and all of a sudden they are coming up short on the angle. next thing they know they are at a bad angle and fighting to aim the trailer in the hole with a bad set up.

As far as the fifth wheel goes those 10 inches or so don't make worth risking a fairing because you shorten up. If anything a bigger space between fairing and trailer helps because you can get greater than 90 degrees if you need to.

Hope this is useful to someone

 

I backed into a dock where the tractor was 90 degrees to the trailer after I was at the dock. I was delivering large coils of copper wire. I crank down my landing gear and the shipper starting giving me a hard time, saying, "You can't drop your trailer."
I told him I wasn't dropping, I crank down the gear to stabilize the trailer.
He didn't get it. I explained that at 90 degrees the trailer will lean from the weight of the fork lift, because the fifth wheel pivots. He still didn't get it.