first of all iv'ing 120mg of k is relatively pointless, a waste of k, and with a dose that high you're likely to not remember your trip. second, if you iv k, you will not be able to hit again with another iv immediately afterwards unless you're a super pro, and even then it's most likely to miss (you just wont realize it cause you'll be too k'ed out). if anything you should mix the dmt with the K if you plan on taking them together. third, i find that my hallucinations were actually STRONGER and more visual with IM k than with IV K; probably because it comes on too strong with IV K, that most of it ends up getting blocked off in the memory. last, iv k is about as addictive as it gets (for me anyway). once i take the first dose, i dont quit until the vial is EMPTY.
i too have injected 5-meo but i did this in combination with cocaine, oxy, and k (what a coincidence). from what i remember it added hallucinations to the ketamine trip (the main focus of my trip).
If you ever get ahold of DPT, do an IM shot with K--you'll be doing yourself a huge favor :D