I took a look at plans for the pacer and the wings have a flat bottom with a positive incidence, both conducive to a high climb rate.
This configuration is made to climb with a increase in air speed (normal) I believe it was designed as a free flighter also, but over powered and not closely monitored you will get what you got.
down thrust will help but maintaining a proper angle of attack is the way to go.

ALL day dan
your wing appears to be of the symetrical type and shouldn't exhibit the high climb tendencies of the sterling kit.