If you want real security, spend the $70-80 for M780s. You can set the release to where you will never come out accidentally.

I don't skid but I have been known to go downhill really fast; fast enough that I have no idea where my heels are. (And I tend to rotate them in going around corners.) The M780s are the first clipless pedal I have ever trusted riding fixed in my usual fashion. And I still won't go quite as fast as I might with straps. I have been riding toeclips, quality leather straps and aluminum slotted cleats for decades. Pulled tight and with cleats in good shape, I trust that combo. I really like the redundancy. Pull a cleat out at speed and my foot is still in the clip. Slow down. Get that cleat back in, get that heart out of my mouth and continue, intact!

Ben