I have been trying to finish off the right pod.
I ended up removing the angle of the decoder, and moving the location of the equipment more towards the wall to allows the TT to fit in the end.
Amp tucked away.
I even managed to wire everything together.
The idea behind the patch panel is that it allows me to change what goes where very easily.
I can try the surround L/R rather than the front or swap the sub and the centre over.
And as one EQ has the RTA on it, I can even change which channel goes to which EQ to see what gives the best result.
But the best thing is that there has been a few session using it all in anger. The verdict? It works

I am getting the passing of the rumble strips from left to right, when you come up behind a car you get the full force of its exhaust and with the right car you even get road rumble at just the right level.
What I have also discovered is how variable it all is. Never mind from car to car or track to track, the level of the effect varies just doing a lap. It is most frustrating. When it all comes together it is amazing, the extra level it gives may not help shaving off seconds on a lap time but the immersion is priceless.
However, now there will have to be loads of playing / testing / tweaking; joy!
Had the local building inspector round too, checking up to make sure all is within code.
One of the reasons the TT seems to be so much better might be do with me now having attached the TTs directly to the seat.
I still have the last one to mount to the rear of the seat.
Then I will have to see which works best on which channel. I am also going to have to duplicate a channel for the sub to hang off. Although the small EQ does have a sub out, so I could link the sub to the centre (the right channel of the EQ) and see how that feels.