I'm sure someone else will chime in, but ...
Use Drill Rod instead (McMaster-Carr among other suppliers). To the uninitiated, the name makes you think of high speed twist drills who are as hard as the devil and just as brittle. But not so grasshopper - the name comes from the diameter sizing of the round wire, using AWG (American Wire Gauge) specs. To put that in perspective, if you have, or are familiar with a 1 - 60 drill index, you have access to all the pertinent sizes we can use to tighten up or free up hinges on our cowling (as well as flaps - if need be).
For the standard (.090) hinge pins, there are three sizes that may be of help - #46 - .081", #45 - .082" & #46 - .086". For the .125" hinges that go on the upper cowling, where typically the pin that comes with the hinge just won't go around the corner, here are the sizes that can help (reduce the freeplay of a .090" pin), #36 - .106", #35 - 110", #34 - .111", #33 - .113", #32 - .116" & #31 - .120".
Because the sizes are so close together, you can also size "up", as your hinges wear in over time, and recover some of the "looseness" that just comes with time in service.
For the "truth in advertising" part - drill rod is not as "stiff" as the .090" pin material. So, it can be bent if you are not careful with it - but I have used it for more than 30 years in my -4, and Rocket, and have never had to replace one for a bending failure. Replaced them as conditions allowed for "sizing up" - but o/w, no failures.
So there is a path out there for tightening up those loose ones if you choose.
HFS
As an addendum - In my experience I have seen a lot of "sag" over time in cowlings mounted with the undersized pin; and, when building you would (should) have already allowed for a paint "gap" for the future ...