That's been the limit some of us set as a max weight on a packraft. And now I am there.
My 2011 Llama came heavy, with its extra heavy duty spray deck, made from fabric nearly as beefy as the tubes, plus a fat four inches of velcro down its tall waist-wrap. It arrived weighing around 7 pounds.
Then I added a thick poly-pro line to the bow and stern so I don't get separated from my boat like this guy does. In the past, the "chicken line" went right round, but for creeking, just fixing the four front together with poly-pro and the back two seems both necessary and sufficient.
All last season it had beefy metal D-rings for thigh straps fore and aft, anchoring thick, padded Aire Deluxe Thigh Straps. I added sticky-back velcro stabond-glued on the inside tubes to hold an early 2000's style seat as a beefy backrest. This brought it up to over eight pounds
And most recently, in anticipation of creeking on long slides and big drops back East, I added a cut-to fit 1/2 inch closed cell foam lining, a 12" x 12" minicell pad under the stock seat and an 8"x8" foot pad.
The next mod may well be replacing the thigh straps with knee cups, which may take it back down again.