I have a similar setup on my 1-ton and it has worked well for 30 odd years. Back in the day I lived with a friend who was hauling water from the town well with his 3100 when his well went dry. That had lots of additional spring leaves. He had a clean 325 gal oil tank in the back. After a couple of weeks of this the frame cracked between the spring hangers. So we began using my 3800. I added a couple of leaves from the bone yard to the overloads for that job. If they're too stiff you can take a leaf out or if too weak add a leaf. I've been doing that for decades as load requirements changed with no problems other than that I shook a camper apart before I came to my senses and removed a couple of leaves. It was far easier to do that than fix the camper, which took a couple of weeks with glue and a table saw.
The 1-T frame is heavier so I have had no problem with any twisting or flexing but the auxiliary springs were an RPO option on 3800s and were not on 3600s according to my spec book for '51. There was probably a reason.
