I took the new trike for a spin yesterday, then a longer ride of a few kilometers. Here is what I can report. (photo's attached)
For anyone considering building a TT clone, Laurent Dechenne's Speculoos drive train worked flawlessly. There is very little if any peddle induced steering. That being said, there are few problems with my implementation of it. Basically its just too heavy, and this creates a fair bit of inertia, that makes the steering a little less responsive than my liking. If I build one again, I would strip the weight right back, by using lighter profiles and less metal.
As for the self centering effect. It works! When you ride along in a straight line, it feels like regular trike, holding you level. When you go into a corner, and start to lean, you generally lean all the way over until you hit the tilt lock, and then if you need to you just lean a bit further out and you can take fairly sharp corners comfortably at high speeds -- certainly faster than I would attempt on a regular trike.
There is also no noticeable influence from road camber, and the rear end actually makes riding over uneven surfaces smoother. At one stage when I was turning around the rear outside wheel clipped the edge of our driveway and rode up onto the curb, then bounced off, all while I was at full tilt, and it had almost no influence on my steering line. I actually did it again deliberately just to see.
All that being said, I now think that the Speculoos drive train is actually a poor choice for this trike. With Laurent's geometry, the seat height is supposed to be equal to the BB-Height. It turns out that this is just simply too hight for my self centering geometry. My seat is currently 340mm, but really needs to be 250mm. The self centering effect, only worked when I took the seat frame off, and put a sheet of ply on the frame, and rode around sitting rather uncomfortably on that. With the regular higher seat, the self centering effect doesn't work at all, and actually makes the low speed stability very tricky. However, with the lower seat hight, pedal induced steering was noticeable.
So it looks like I will be chopping the front off and replacing it with my original Python drive train -- don't any one say "I told you so" :-D