Has anyone here used heavy carries and heavy sandbag shouldering to grow their upper back?

I have been doing 531 (predominantly bbb, occasionally beefcake when I can) for the past four years. I have noticed significant gains in strength and size (I've gone from 160 pounds to 200 pounds at 5'11"), but I have also noticed that my lower body continues to outpace my upper body in size.

I have always been fairly bottom heavy, but it feels like it's gotten even more pronounced over the past year. I've been incorporating more dumbbell rowing and weighted pullups as accessory work (and occasionally as main lifts) into my routine (twice a week each, never on the same day), but it doesn't seem to have much of an effect.

I spoke to a friend recently who suggested heavy carries and heavy sandbag shouldering. He said that they absolutely blew up his back. He offered to give me some old farmers handles and sandbags (150 pounds and 200 pounds) that he wasn't using.

I'm intrigued, but I don't have a lot of space at my place presently to store them (though I have a large, flat yard), so I wanted to get some other opinions on whether it would be worthwhile to try them out.

Can anyone on here vouch for heavy carries and heavy sandbag shouldering growing their upper back?