Have been using my homemade centre handle made of nylon rope in a soft plastic corregated tube that's normally used for boat bilge pumps.
Also changed the leash for a Naish wrist leash that has been extended with about a 50cm long outdoor blind chord tied to the front handle.
After about 5 sessions still happy with the add on.
With the centre handles I don't need monkey arms to reach the rear handle which was sometimes missed when the wing sways which wasted time or even caused me to fall off the board as I don't do knee starts. It's quite easy to grab the centre handle & make the quick transition to the rear handle.
And the longer leash makes it much easier to clear the wing after a fall when resetting for another run.
No problems packing the wing up & putting it in the bag.