Is the point of the plastic cage on the T400 just to house the reflectors? And maybe to provide some surrounding support to the rest of thes shoe? There's an implication, in some AI answer, that the big cage enables you to ride in ordinary shoes. But that sounds like nonsense to me.
Did the T421 not hang in a predictable way? I've found that with the T8000 it reliably hangs with the SPD clip facing backwards, at least after the bearings had loosened a bit. So now it's second nature to "kick" it forward to clip in, or backwards if I'm on flats. Shame, they're good pedals, but I really don't want another pound of flesh ripping off my shins again by those pins.