i've only made brownies once.. i used an ounce of reggie buds, and a shit ton of trim, and used two sticks of butter, and holy fucking shit.. the first time i ate three of them and was wrecked for about 15 hours or so.. totally couldn't sleep as i felt like i was tripping on shrooms.. woke up and looked into the mirror and it had looked like i was literally run over by a train, lol.. those things were scary strong.. i gave one to a guy at work, and he was afraid to take another one after eating the first one, lol..
and i agree with the op, the hangover from strong brownies can be crazy strong.. i was in amsterdam and ate some space cakes that said that they had .5 grams of hash per brownie, and i felt not a damn thing from them, so when i made my own, i figured that i wouldn't really feel too much from them either.. big mistake, lol... eating thc can wreck you if potent, lol..