:::chuckle::: I'm about 5'7" (I've shrunk over time), a bit broad in the shoulders for a woman, and in reasonable health. '
I do the following if I have a marginal backpack (as my 36L 5.11 Tactical Skylight will be, based on my taping it, as well as the advertised sizing -it's a small/medium).
I check in online now, or use the kiosk. I stay away from airlines and airfares that charge extra for carry ons. If my flight's on one of those, no backpack, or I check it.
I wear a shirt that closely matches the strap colors, and have my small personal item very clearly in my hand (it's usually black or blue). As others have mentioned, that item holds as much of the bulky backpack contents as I can manage, plus anything I need to have access to during the flight.
I don't try this with something that super obviously won't fit in the box, as in, you can see the pack outlines if you're facing me. If the pack is visible past your outline, they're gonna want you to put it in the box.
Once past security, and while I'm in sight of the gate attendants, I'm standing facing them. Not hunched over, not struggling with the weight, and by all that's holy, not rummaging or fiddling with the pack.
Calmly walk on, greet the attendant, make my way to my seat, stow the backpack overhead myself, not needing assistance.
Again, I can usually pull this off because I'm taller-ish (so the backpack looks smaller) and strong enough to stow it myself. If these conditions don't match your experience, your mileage will vary.