Hi,
I have one of these that we use on our splitter purchased from Loews, and it works very well.
I initially drilled and tapped a hole in the back of the splitter's wedge to hold it on, but the bolt
broke off very quickly in normal mild use, so now we just use it in the slip-fit fashion, which is good because it allows some slop, and it is easily removed if we want to just use the main wedge, which can be very helpful in splitting large or stubborn knots or really twisty wood.
YMMV,
PA
FWIW, I believe the backstrap on it that fits around the splitter's wedge is either 1/4" or [less likely] 3/8"- as all it does is retain the 4-way on the main wedge for the return [decompression] stroke.