Someone on the Ace Thread (I don't know how to tag them, but their screenname is Here Comes A Regular) mentioned that a Slappy hanger fits perfectly on an Ace baseplate, and they work really well together. At the time I happened to be converting a pair of forged Ace baseplates to work with an inverted kingpin (JB Weld holding a kingpin nut under the baseplate), so I figured it was worth a try. Once the JB Weld cured, I set those baseplates up with my hollow Slappy hangers, and that shit changed my life.
I'm not sure if it works better (there may be a placebo effect going on), but it definitely didn't get worse. The turns and grinds felt great, the grind clearance (which was already great) improved dramatically, and everything felt just as stable as before. Also they maintain at the level of tightness I like, and I'm only having to tighten them once every few sessions, which is incredible. I bought a pair of Slappy Trucks after my frustration with my Indy Mids brought me to a breaking point: I had a LOT of lateral kingpin movement with the Indy Mids AND they came loose all the time, which was disappointing because the tech involved with those baseplates seemed like it would solve all of the problems associated with inverted kingpin trucks. Unfortunately they didn't work for me, and from reading around over here, it sounds like they didn't work for a lot of people (including the pros who had their names on those particular type of trucks). The inverted Slappys are a definite upgrade over the Indy Mids, and the addition of the Ace Baseplates were just a fun opportunity to play mad scientist, inspired by the recommendation of a great contributor to this board.
There was nothing wrong with the Slappy baseplates whatsoever, even after about a year's worth of honest wear. Those are now set up on my cruiser, where they are enjoying semi-retirement life. The Ace baseplates just happened to be a little lighter, a little stronger, and looked a lot cooler. I was also happy to see how everyone else loved the look of a black baseplate with a raw hanger, because that happened to be the color configuration I ended up with.
I am still curious about those new forged Slappy baseplates. If Slappy offers them in black, with a raw hollow hanger, and an inverted kingpin option, I'll have money ready.