I have seen a couple pictures, but nothing in person. From what I have seen, it's a matter of finding some good tubing with an ID, the same or very close to the same as the OD on your stock frame tube. Cut the stock tube. under the seat skirt area. Side the new tubing over the original and weld the ends. I would run a gusset from about 3 inches before, to about 3 inches after the new tubing. ORRRRR, if your trike is in good condition, you could sell it and find one of the many adult size trike that are currently available.