I started out with the M520's after having mks sylvans. They were a great improvement and I was skidding right away. Never popped out. If anything I probably had them tensioned to high.
After about 1500 miles I switched to the shimano 5700 sl and I have been skidding fine with no chance of a pop out.
I left the setting low like they were set. So I think as long as your form is good you should not have a problem.

I would trust being brakeless with clipless over straps and cages any day.