I haven't had a chance to ride the Casseroll with that size load. My normal full load for touring is 25 -30 lbs on a Surly LHT. The Surly is certainly a heavier and stiffer frame, and I'm not sure how well the Casseroll would handle something like 40 lbs. I anticipate using the Casseroll when my loads are under 20 lbs. I've read some post on MTBR.com/salsa about the Casseroll and heavier loads. But I'm not sure those were from experiences with the new Casseroll or the last version.