This Pouchlings preschooler full buckle carrier will carry large toddlers into the preschool years and beyond. It has crossable straps (that can be worn rucksack style) and a padded waistband.
There are more videos and photo tutorials listed on the Carrying Matters website.
The Sheffield Sling Surgery website is here - full of useful information about safety, all sorts of articles about warm/cold weather carrying. knee to knee support, big kid carrying and so on
Facebook page is here and the online support group the Virtual Sling Surgery is here