Oh yea, the DPH was really unnecessary with the 2C-I and I would suggest when you do it again to skip the DPH. Perhaps that is what made it feel so "flat" for you. 2C-I really has no body-load except for stimulation, but that is part of what makes it work.
2C-E is ALOT different. It can cause intense nausea, and widespread very weird overall body aches and pains that can be REALLY uncomfortable for most people. 2C-I does *NONE* of this. Anyway these are why to do DPH with 2C-E. It's unnecessary with 2C-I and might alter the trip more than you want.
I would say wait ONE week, then try 25mg on an EMPTY stomach (no fruit juice or other acidic beverages like soft drinks [look for citric acid on the label], ingested acids lower the potency of all phenethylamines) with no DPH. THATs how to tell what 2C-I is really all about. If you ever smoke weed... have some of that available to accentuate the trip and perhaps smooth over any temporarily excess stimmyness. But if you DO feel "stimmy", don't sweat it... its how you know the drug us working. Ever done MDMA? There is a period of stimmyness the first hour or so... (with 2C-I about 1.5 hours)... which then melts away to reveal the drug's psychedelic effects like the drawing of a curtain. A beer with its hops and alcohol is also fine and would also be good for the stimmyness.
Unless you are like me and find a mental way to ENJOY the stimulation, like an exciting carnival ride... just try to relax and breathe deep and enjoy the "liftoff" like you are in the "Booster" phase of taking off in a space rocket. Dont psyche-out and start to panic.... it will melt away soon enough, just ride it out and you will be rewarded. If you panic and start to freak like some people, well then all bets are off. A good way to take your mind off it is to watch some exciting or trippy movie that you can let yourself be absorbed into, smoke a joint, etc... you'll be fine based on your report above. Good luck!!
Heres a graphic they used to play at peak intense psychedelic moments of Grateful Dead shows, spelling out NAMASTE in Sanskrit... try to stare at it for a whilefull-screen in a dark room when peaking, haha!