Never made one...nor ever crocheted! So can't help there I am afraid, except to suggest that at over 10kg you really don't want *any* stretch in the fabric at all, it needs to be solid to give you the support - and bubs the support - you both need to wear comfortably and safely. Like I said, I've never crocheted, but not sure if a crocheted carrier will give you that support at his age and weight now.

But yes, a ring sling is perfect for hip carries.