I built my ZP-38 per the plans with 4/40 pushrods and Sullivan clevices of all 4 flaps. One servo per flap. 4 years and over 100 flights and never had a problem. If I had to set it up again I would use a JR Matchbox. What a pain it was seting up 4 servos to all work the same. PS use a high tourqe servo if you want them to come down under a load. Mike