Will the MADCO work with Kuryakyn grips?
Yes. Here is a picture from his website (on Hondas).

I have two sets of them on my interstates. It's been years, since I put them on. Remember, the Kuryakyn ISO grips specific for Valkyrie are like 6 1/2 inches long. And the throttle boss (above the grip) uses up a bit of handlebar. I believe the kit comes with that plastic spacer (to screw into the bottom of the throttle sleeve), so you don't end up with a half or three-quarter inch of empty ISO grip on the ends.
Now if you have a standard set of Universal ISO grips that are 5 3/4" long (which also fit Valks), you won't need the spacer.
Notice in the picture the length difference in the stock (plain) vs Kury ISO grips (which are the long ones).
I always recommend not adding any extra weight to your bike key, the weight and wind adversely affect the Valk ignition switch over time. But that little aluminum hex key (to adjust the throttle lock tightness) weighs a couple grams, and is on a ring on my valk ignition key, to keep it handy (and not get lost).
Over time, it needs snugged up just a bit.