The very first thing we did when we received our K9 Sport Sack was strap in and go for a short trek around the block! Getting Imogen Bean strapped in was a fun game for her, but once she realized what we were doing, she bought in 100%. The only concern I've had so far is getting the backpack onto my shoulders once she's in - it takes a little bit of extra care and focus to make sure I don't swing her or let her flop over - but once the backpack is on my shoulders, it's an absolute delight. She is snug and comfortable, excited to experience the world from this new vantage point, and doesn't wiggle or fight at all, beyond the occasional rump/back leg shift.
The straps are placed appropriately for her body shape. They reinforce and appropriately support her and are comfortable for the way she rests in the Sport Sack.
She loves loves loves to go on walks and spending time with me, but gets distracted easily and eventually decides that it's more interesting for her to sniff random trees and try to dig and lay down in the grass than it is to walk, so this backpack is the perfect thing to extend our little adventures.