HOME IT Adjustable Bed Risers - Elevation in 3, 5 or 8 Inch - Heavy Duty Stackable Furniture Risers Supports 1,300 lbs - for Under-Bed Storage, College Dorms, Table and Couch, 4 Pack White

We raised the overall crib height (while mattress was at a low or even lowest setting) by using these risers that go under each foot of the crib (there are other variants and brands available) : HOME IT Adjustable Bed Risers - Elevation in 3, 5 or 8 Inch - Heavy Duty Stackable Furniture Risers Supports 1,300 lbs - for Under-Bed Storage, College Dorms, Table and Couch, 4 Pack White https://a.co/d/0fG11O3q We used this for both of our kids.