In Caio Terra's new half guard set, when he addresses the quarter guard, he makes the point to not cross your feet, but keep them parallel while squeezing your knees. He claims this is a far tighter squeeze than you can get with your ankles crossed. I haven't messed with it a ton, as my natural instinct is to cross my ankles, and I always forget in the moment. But I definitely agree with Harry, in that my quarter guard is much more closely linked to my deep half and reverse de la riva position, but I don't play lockdown personally.