I much prefer to use hardwood pushrods, or arrow shafts or carbon fiber tubes for pushrods. Balsa was popular for pushrods in the past as with a trainer the pushrod would likely give and break before damaging the servo. Nowadays it can be hard sometimes to choose a good piece of balsa for pushrods as the stores may not have a good piece to use for that purpose. The balsa is hard and heavier than light balsa, almost like it is hardwood. So it is much easier to go with spruce or pine or something for the pushrods.

Servo trays don't usually come with radio systems anymore. The stores may or may not have them anymore in stock either. But it is quite easy to make your own though. I like to take two pieces of 1/8 inch model aircraft plywood and glue it together to make a 1/4 inch thick piece and then use this for the servo trays or servo mounts. The multi-layer plywood doesn't split easily, when you insert the servo screws, and is more stiff than the plastic servo trays. I usually cut out some 3/4 inch wide strips of 1/8 inch plywood and glue them together. Then later I cut them to length and mount the servos on them and glue the servos and wood into place in the fuselage.