Can you field load 13' 6" trailer

Most of the combines these days would be able to off load into a trailer that high, yes. Grain carts are that tall and some are slightly taller.

However the grain cart may have difficulty off loading into a trailer that tall. If it would reach that high, it may not unload the grain directly into the center of the trailer. Just depends on the brand or make of grain cart being used.

Another thought is if it’s wet to get into the field and they load on the road. Most roads have a crown and will tip the hopper away from the grain cart, changing the angle again of how the grain cart can unload into the hopper. Just something else to keep in mind.

Best thing you could do is talk to the guys with the equipment before you haul and find out how tall that grain cart can reach.

Yes you can but you need an open mind. I personally had issues 1 time with grain buggy not clearing so i had to drop air out and we laid some planks on the ground for the buggy to pull on. it doesn't take many planks at all if you only put them under the wheel towards the trailer. That kind of physics you cant learn in school.