I think for the reasons svcontinents cited, 25" is plenty big for handlers.
And, oh, by the way, we have never had any GCT PD get us porters to get our luggage off the airline belts. The GCT people were always outside Customs waiting for us, mostly the bus driver or maybe a local GCT person, greeting us and directing us to the bus, to which we each carried our own suitcases, other travelers from our flight as well. In Europe or Asia, most airports have carts readily available at the baggage area, free of charge to get your bags to the bus.
And, yes, once with GCT we didn't have to handle the bags again, except to take them off the bed after packing and out the door for pick-up. Remember, too, if the bell boys just put your bags in your room when you are still out on vicinity walk, are you able to lift the bag onto the bed/rack to unpack? 25" is heavy enough.
Lightweight clothes, stretch jeans, cotton long sleeve jerseys, acrylic sweaters, windbreakers with lining all are lighter than heavy cotton sweaters, heavy denim jeans, and fleece jackets. GCT trips are mostly no dress-up, even on river cruises, so leave fancy stuff at home. Take sundry items out of boxes, make smaller bottles of tablets or buy blister packs; medications in small zipper plastic bags from pharmacy areas, instead of bottles of medicine. I carry list of medications, dosage, and taking info; TSA doesn't require original bottles and my list is readily avail. in case they ask. For things like aspirin, allergy meds, stomach aids, etc., I use those same small zipper plastic bags, these usually go in large suitcase. Cold meds come in gel caps now, so liquid bottles aren't necessary. Lots of ways to cut back on weight. E-reader rather than 8 books. Some people like feel of book in their hand, leave that for your leisure at home.
I'm getting so good, I've gone from 49 lbs suitcase to 41-43 lbs.
Be sure to carry one change of clothes and underwear in your carry on in case luggage is lost. Then at least you'll have two sets of clothes. And put windbreaker at least in carry on, or as most travel tip sites state, wear heaviest coat. Me, I put that in the suitcase and have an extra sweater/long sleeve jersey in carry on instead, little lighter.