Technical Front Shackles Question

Yeah, I was gonna say, unless we have seen excessive play or "smoking" of the bushings, it's not really a fail. I'm trying to imagine what the additional amount of play at the bushing would do that isn't obvious since the bushing operates in the same plane.

 

Dummy in the back here.
I'd guess there is a very slight force that isn't normal on the bushing on the axle perch. Probably nothing more than a slightly wider wear area.
I'd also guess that since most cars with a transverse spring have packaging issues with this type of mount, that could be why it's not common. Either a tight fender or a radiator support is in this area in a lot of cases.
I'd also guess that the 'never used on factory cars' has more to do with the period of time a transverse spring and tube shocks were both regularly used by the same manufacturer. I'm no historian either, so I tried to find info.
This points to Ford still using lever shocks in 47. So my question is, when did Ford start using tube shocks, since the other brands didn't use the transverse spring this late?
https://www.fordbarn.com/forum/showthread.php?t=215792
As for the possible shock causing spring to travel sideways (rock) in the shackles, it seems the rain grooves in the road would exert much more force, which is a known condition. As mentioned, most shocks can be opened and closed by hand, a much smaller force. A panhard rod could handle this if it was determined to actually be an issue.
Since @2OLD2FAST EDIT: @swade41 has the only voiced experience with this, I'd go with his known quantity over any guesses, including mine. He has proven to be a knowledgeable member here on other things, so I tend to agree with him on tech. EDIT: Feel the same about both members!

 

Swade41 said he had them on his car . California Custom Roadsters sells this type mount as does speedway motors , on a couple Tbucket sites you'll see these being used , successfully .

 

If it had a bearing instead of a rubber bushing it likely would not be an issue.

When the lower mount is attached to a control arm, or similar, the twist of that bushing is only a few degrees in either direction throughout the complete suspension cycle.

When attached to the shackle, that twist is increased in degree, and radically increased in frequency.

 

Seeing as how you feel this rotational problem is so critical , I'd suggest you do a complete engineering study on it to keep us all from such a grave danger .