There are people trying out solutions that are less expensive in the EU. I can share their results once they have installed them.
I can already base some of what I said from past trials. Very much may depend on the spring type used, if guide rails are even needed to stabilise more the seat/pedal sections for a motion rig. Not just apply an additional element to the types of springs you/others may have used.
Thoughts:
If wanting or having the tactile operational from a motion based option, the contact from the guide rails to the main plate like you illustrate in your own build. This would help that transfer into the seat as it is now, no longer necessarily having to go up through the springs/dampening used to reach the user.
This works both ways, as from the other perspective of the additional tactile energy being maintained in the seat. It now has a contact path and more potential to then leak into the main rig frame, also now bypassing the springs/dampening.
With larger units like the BK installed to the plate the wider "low bass bandwidth energy" from these will still most likely encompass the seat. May need some varation to the volumes to compensate... The query I would have is, how much this might affect different or higher based frequencies from a model like the TST that have less bandwidth.
Another factor is how well, the tactile from both sources can be made to operate together, (if people want that)..What from the motion based tactile, can we not improve via Simhub based effects and additional tactile we can install direct to the seat and pedals?
Very much depends on what the user has or applies in effects, what they want or like? You wanted to reduce the number of active effects to the Simhub tactile but with this you will likely loose potential stereo abilities in effects. To some this may not matter, for me it is something that has not been fully explored and I can illustrate soon what it can offer.
The fact remains that Simhub has multiple stereo based effects and few people I believe have made effects that combine them to operate together. Motion based tactile (as I understand) is usually only mono? So these are just elements to ponder.
With Simhub, it is possible to reduce the number of active effects per channel, and improve upon previous tried options that were used. By now using 6x - 8x BDS units attached to a seat will set a new level of potential.
Currently no other transducer/exciter can be attached direct to a seat in such numbers that operates the way it does or achieves quite what we can do with utilising low/mid/high bass. This all in a single direct to body based unit, and with that it brings improved potential with the stereo sensations. These could be implemented into effects as an option based on user preferences, to either use or just apply something different with what effects they want.
In a fascinating way.....
Tactile will always have different users possibly preferring to use or do different things and in different approaches. So always good to see how others come at it with different methods or perspectives. I still have things I want to do in my own build that I have not yet seen applied with tactile, but really the only way to know is by experimenting and putting ideas to the test...