here's my input, and i've said it many times before:
i was used to taking 350 mg of DXM and then smoking weed on the come up. i had lots of fun times with this, and the experience was always good.
one day i figured i could do 700mg and smoke during the come up. BIG mistake. i was so fucked i can't even explain. the entire room had this sort of static about it, and everything felt foreign. i felt like i was going to die, and i can't even describe the feelings that went through my body. i kept warping in and out of worm holes when i'd lay back and close my eyes, and it was very frightening for me. i had to have my roommates try and calm me down, and i literally thought i had to go to the hospital and that i was going to die (if it hadn't been that i read on erowid earlier that day that kids wind up there all the time for accidental "overdoses" (not acetaminophen overdoses, but just taking too much DXM and freaking out overdoses) i'm sure i would have had someone drive me). i eventually ended up in my bed and i went on some crazy ass journeys in my mind, and experienced some crazy ass closed eyed visuals, while continuously warping.
whenever ur comboing weed and DXM, make sure you start slowly, cuz there can be a huge difference when you double your dose and add a lil weed on top of it. i feel like i just need to write a trip report about my experience so that i can just provide a link whenever i give my advice concerning people dosing DXM.
trust me, things can get way more intense than you wanted them too. i also experienced significant body load, and it was like my heart was going to jump out of my body, and i kept feeling like i was going to die. i was alone in my room (altho it had a very foreign feel to it) freaking out the entire night, and the experience was not pleasant.
i wish you the best of luck OP. tread carefully with DXM. if i didn't have my roommates to help calm me down at times, there's no telling what i would have done.