You got it. say if your airplane weights 20 lbs just divide it by 4 and the sum is 5 lbs of thrust to get 1 to 1 weight to thrust ratio.
but you won't actually acheive 1 to 1 with this size airplane and the engine type. you would have to run 60 size engines and the wings would ripe off lol. So im guessing that your airplane will weight about 21lbs with batteries so i'd try to get about 16 to 18 lbs of thrust out of your engines and play with prop sizes.