Currently when sending dwellers into the Wasteland, the maximum Stimpack and Radaway carry capacity is twenty-five each. Is there a way to raise this capacity?
Reading on the GameFAQs forums here and here, the answer at first appears to be "no", but the information is also two years old. However, the first mentioned a potential exploit that once existed but has since been "patched out"; I believe said exploit is what is referred to in this article. Investigating the Bethesda community forums for Fallout Shelter, I was unable to find anything particularly relevant to the specific question.
So: Is there either a) an in-game mechanic for increasing wasteland carry capacity for stimpacks/radaway, similar to Strength allowing the increase of loot carry capacity, or b) a new exploit that allows for the same function as the patched-out one?