This is a subject you guys actually changed my mind on. Never really ran any monster springs, but i used to break in with milder doubles and was successful. Thanks to the stories and expertise here, i don't think i would try it now days. Ironic that the only failure i had, and i caught it early, was on a SBC with a Crower 460" / 218*@.050 hyd. with singles and that was 1,000 mi in from a no spin lifter.....lol.