I have zero personal experience with either substance but I just thought I'd chip in my initial reaction to your idea - stimulant + stimulant is already a dangerous combination, even with tried and tested old school stimulants that are really well known. Mixing two relatively new research chemical stimulants, both of which are sufficiently new that literally the very best we know about it's pharmacological activity comes from users making educated guesses based on its effect profile is asking for trouble.
If you aren't fond of either substance then I would flush both of them, cut your losses and move on. If you aren't willing to do that my next suggestion would just be to take one of them in one session and save the rest for the next. I know next to nothing about dimethocaine but I know the PVP is notoriously more-ish, so if you're going to do that and you only have a small amount I would seriously consider getting rid of the dimethocaine first (not by consuming it!!) or at least arranging it so it isn't accessible/in your possession at the time, because if you're fiending hard for another line of peevee it would be all too easy to get started on the dimethocaine. And honestly in my experience if I don't enjoy substance A and I don't enjoy substance B then I've never found that I magically enjoy A+B, if anything I've found that shitty drugs mixed together make for an even shittier experience than either alone. And if not enjoying yourself was the only problem here, I'd say by all means go for it. But it's possible that very, very, very few people have combined these, and it could potentially be disastrous. Their combined effect on your heart rate or your blood pressure could potentially be extremely dangerous or even life-threatening. Do you really want to risk death for what is probably going to be a shitty high? I know you've already bought them, but if I were you and I wanted a good stimulant experience, I'd sell what I had and just buy a tried and tested decent stimulant, like amphetamine or cocaine or even mephedrone, and what I certainly wouldn't do is mix two research chemicals that aren't even good on their own. Plus, what do you know about the serotonergic activity of either? I am vaguely aware that the PVP doesn't have a huge serotonergic effect, or just a small one, but even two chemicals that only have a little effect on serotonin when mixed together but you at risk for the potentially fatal serotonin syndrome (thus why St John's Wort has been implicated in fatalities from the condition in the past).
However, if you are totally dead-set on mixing them both, then you should at the very least start with very, very, very low doses of both, much lower than you know you can handle of each alone, and go very very slowly, working your way up in tiny, tiny incremental doses, and resisting the temptation to take large doses of each if you get a sub-standard buzz. More knowledgeable members can correct this if I'm wrong, but I would say the safest ROA in this situation is via snorting, as you can gauge the amounts easier and the quicker onset of action means that you can titer the dose upwards very slowly and make it slightly less risky. Definitely always be aware of the effect it is having on you, and your heart especially - if your heart beat accelerates past what is usual for when you're on either stimulant, I would definitely at that point cease dosing entirely. Maybe have a fast-acting benzo on hand for the worst case scenario, and for God's sake be fucking careful dude!
