I like to adjust my expander die close to where I want it with the plug screwed into the top and not the powder drop. I've noticed with my 38/357 expander die that the expanding plug is larger than the inside of a case for most of it's length. The result being that the entire expanding plug is performing some expanding of the case and creating more friction when dropping the ram. If this was a concern, I would take it out and polish the straight section down. But I like that I can seat lead bullets with a minimum amount of flare. There still seems to be adequate tension and crimping is going to prevent the bullet from moving anyway.
CAUTION: THE FOLLOWING CONTAINS LOAD DATA THAT EXCEEDS PUBLISHED DATA. USE AT YOUR OWN RISK.
I shoot 148 WC in 38 and 357 cases. The available free case volume is about 13% more in a 357. I've found I need to increase my powder about 10% when loading 357 cases. Start with a load that is safe in YOUR 38 cases and work up from there. Make sure you are checking for bullets that did not exit the bore while working up the 148 WC 357 loads.