That's similar to my situation, except I was taking half as much kratom as you. I tried 2.5 7oh first time, then tried 2.5 plus a little Kratom powder. ( Obviously I'm lightweight in my dosing but that's how I try to keep it). It packed more of a punch than the kratom but seemed short acting , though the added kratom an hour later gave me some legs. I felt some real craving for it and decided to take a break. I haven't thrown the rest out but I've held off for 1 1/2 months so far. I like the high but I don't like craving, I don't need that, plus I think it fucks with my tolerance to kratom. I personally think I need to keep it as a rare thing.
I'm guessing some brands are stronger 7 oh than others so maybe just try 2.5 just to get a feel for it, but 5 is ok I imagine.
As for risks, you've probably read what a lot of people have been saying about it. My position is one of being wary, I'm a cautious dude, but ymmv