Can you suggest the best carriers for wearing a toddler on your back? I have a 16 month old and have tried putting him on my back in his catbird baby pikkolo, but neither us of was very comfortable. I also tried a lightweight frame backpack, the kokopax, which also wasn't a good fit for us. Any suggestions?
Are you using the support belt with the Pikkolo? That would be the first thing I'd try if you haven't already.
Soft structured/buckle carriers are like shoes or jeans -- what fits one person might not fit another. Fit and comfort depend a lot on your height and body build as well as your individual preferences. If you have a local baby carrier retailer or a local babywearing group, I'd see what brands they have that you can try on before you buy another carrier. If you post on the Babywearing forum here at Mothering.com with some more details on your physical build, you can get responses from other mamas as to what's worked or not worked for them.
There are a lot of great brands of buckle carriers out there, and I don't want to endorse one over another without knowing more about your particular situation, but I've found that of the generally available brands (i.e. not custom carriers), the Pikkolo, Ergo Baby Carrier, Boba Baby Carrier, Patapum, and BabyHawk Oh Snap! all tend to fit a fairly wide range of body shapes and sizes. The AngelPack LX, Calyx, and Beco Butterfly are good choices for petite mamas or those with narrow shoulders, while the Ergo Sport and BabyHawk Oh Snap often work well for mamas on the fluffier/bigger side.