I hope I'm not too late in giving my 2 cents!
I saw Scott's question and zeroed in on it, so I want to share my experience having had a Celltei pak-o-bird for Boomer from 2013 to 2015.
Can it be worn safely in the front? For me, no. The top juts out and with the stiff material, it was uncomfortable on my neck and chin. Further, it is more rocky/unstable for the bird versus having it hang from your back.
I liked the pak for the 1st year. Very convenient and not too shabby looking. But after the 1st year, maybe less, the front stainless steel mesh started caving in big time. So that it was taking up room in Boomer's perch area. Then the walls and the roof started caving in. Then the back and bottom started warping. I got the size small so you'd think it would hold its shape more but the material is heavy canvass + flexible plastic inside corners. The structure is not strong enough to hold its shape after a few months to a year.
By 2016 it was unusable. It just sat in my closet where it started a colony of weird insects until I threw it out. It's easy enough to wipe down but impossible to do a deep clean without ruining it. I took care of it by putting down extra towels to catch poops, but with the food and Boomer preferring to stay at the bottom instead of his perch, things got messy inside especially on longer walks.
That's yet another thing. Boomer would perch on it when we're stationary but the walking motion was uncomfortable for him to stay on the perch so he'd hang out at the bottom with the poo-poos. I thought maybe walking was okay because it would mimic the sway of branches in the wind, but that was not our experience.
For the high price, I expected many years of use. I used mine maybe 2x to 3x every other month for a year until it became uncomfortable for Boomer. Hopefully another manufacturer offers an option. I don't see comparable ones in Amazon, albeit last time I checked was 8 months ago. Without competition, I don't see Celltei wanting to improve their product or lower their cost.