OK for the HK trucks, here is what I found and suggest.
Nicely made with some interesting design features that may help (reinforcing rib boardside) and may hurt (gapped bushing seat wall). I found the Stock bushings to be around 94a and severely undersized in diameter for both the cone and the barrel (.915" nom) and undersized in height for the Cone (.428"). The stock king pin diameter is .362" and the king pin hole is drilled .387". When you take all those things together you have a lot of potential slop where the truck does not turn when you go off center. It takes several degrees of angulation for the bushings and king pin to go to the end of their tolerance and start the truck turning. This causes a very uncertain center, like the steering of a 1955 Chevy.
Picture shows the available space for bushing shift in the stock set up:
Compared to the upgraded set up:
Possible upgrades include RipTide bushings and pivot cups. The HK trucks fit our standard longboard Cones, Barrels, Canons and FatCones (boardside only) and our Indy Pivot cups fit perfectly. I also suggest replacing the stock king pin with a AN6-26A aircraft bolt, the bolt alone takes .010" slop out of the set up. It can be purchased at most aircraft supply stores: http://aircraftproducts.wicksaircraft.com/item/aircraft-bolts/bolt-an6-3-8-24-/an6-26a
Here is the stock on left and the fully upgraded truck on the right.
Has anyone experienced cut bushings from the hanger slots in these trucks?