>My greatest concern with the SMC-style anchors (and
>especially anything used as a deadman) is the angle
>of the pull. That is, (in my mind,) my pyramid tarp
>will be pulling hard at an upwards angle of maybe 20-30
I use the SMC T-anchors and stakes as well, and love them. The trick is to attach a loop to their centers (not the top), and to attach that loop to your tent's lines, then keep the plane of the anchor or stake perpendicular to that line when you bury it.
The force is thus handled by the entire face of the anchor or snow stake, and that's a really strong setup. Also, counterintuitively to me, facing the convex side toward the tent works best.
I have a picture of this setup somewhere - if I can find it, I'll post it.