your reference to margin call is important money management consideration - i couldn't use your method exactly as you do because i only have 30:1 leverage - however, this also is also perfect protection for a badly managed trade or catastrophic event - you will NEVER blow your account with a single bad trade, EVER - 30% is the most you will lose!!!
so imagine you are on 50:1 then 50% wiped out, or 100:1 then 100% wiped out, now imagine 300:1, you are in serious trouble...
kc topics: https://www.forexfactory.com/thread/post/14648072#post14648072