Idk about if they are good to take airlayers from, however if your going to cut if off anyways, i would defenatly try to get a new tree out of it. I mean what do you have to loose? Not much. If it can clone, then i'd think you'd have a good chance of getting it to root from an air layer. The other one im not sure, but evergreens are suposidly harder than deciduous trees. If the hackberry is deciduous then you should start the air layer at the end of winter, right before it wakes up, and it would probably be better to leave a few very thin strips instead of cutting full circle around where you want the airlayer to start, this way it will still have some of the cambian layer to supply the upper portion, there is also a wire turnequet method, which is doubling a wire around it and twisting till it bites the branch pretty severly and then adding the sphagnum moss, and plastic wrap. I would however sterilize the sphagnum moss when doing any kind of layering, just to be safe, you can boil in water, or put in a microwave safe bowl, with water, and heat for about 3-5 minutes, making sure it doesn't boil over.

"..If the hackberry is deciduous then you should start the air layer at the end of winter, right before it wakes up"

I don't know where you got this info from, but it is not a very good idea. And will most likely not work at all.

1) If you air layer before there is foliage, there is nothing to provide the sucrose to develop roots.

2) If you "leave thin strips", the wound will just heal over, and not develop roots.

"...this way it will still have some of the cambian layer to supply the upper portion,"

The cambium does not supply the leaves with anything.
The cambium is the pathway for sucrose made by photosynthesis in the leaves, to travel to the roots. The inner core is the pathway up from the roots that supplies water and nutrients to the leaves.

When we sever the cambium, water and nutrients can still reach the leaves who, who in turn send the sucrose developed (energy) back to the roots for storage (down through the cambium). Once this energy reaches the severed section of cambium, it has nowhere to go and collects there. This initiates the formation of roots at that spot.
If the cambium is not entirely severed, there is still a pathway for energy to travel to the roots. And the tree will begin to heal the severed section while still functioning normally.

It is a one way loop -

The best time to air layer is in late spring, after the tree has grown a full set of leaves and the leaves have lignified. This allows time for the development of roots, and removal of the new "tree" to a pot, where it can develop sufficient roots in time for winter.

thanks for the help