Doesn't the 4x1 and 2x1s rub on the outer ring? If I'm wrong I really should be building the base...
I think that's why they use the curved log bricks here though - to guide the inner part of the turntable as it goes round, but with less friction than if they used ordinary bricks.
You do have to watch these parts early on in the build, as once you start to switch on the turntable motor, they did tend to pop off. Once everything is in place I haven't noticed this at all.
There seems to be more pressure on the outer rim since the large wheel is quite firmly pushed against the turntable to keep the speed running consistently. The weakest spots build-wise seem to be the 4 wide tan plates, which have a tendency to 'lift and separate' (rather than wear), and the long blue tiled decorative sections in between each of the tan plate sections. They can pop off and drop under the turntable - annoying - but the protesting clicking as they get run over by the wheel acts as an alert!
The great thing about the build is that, up to about where the first post in my review finishes, it's really easy to lift up the whole ring assembly and fish out any parts that have fallen down or adjust any plates that have come loose. I loved this aspect as I am not a natural Technic builder and find it difficult to 'see' errors that might be obvious to more experienced brains. In that sense, the set is flexible - once the horsies and canopy is in place it is much harder to make adjustments without other bits dropping off!