If they have curbside checking....have a $10 bill CLEARLY visible. Carry the bag to him/her, show the 10 spot. DO NOT GIVE the 10 spot until it clears. Once there, you have to take your chances of curb side again to return home. This always works for me...when my bags weigh 55-60 lbs.
One time the guy came back, "your bag weighs 52 lbs, I am going to have to charge you extra...." Nope... says I, I pull out a spare bag that I always carry, drop 3 pounds out of the number 1 bag. Check 2 bags instead of just the one. Sorry--no tip for being exact. I am sure he learned.