I received my replacement parts from Aires however sadly they sent the EXACT same parts. They don’t seem to understand the issue mentioned in the thread.
Armed with the replacement I decided to experiment trying to get RP3 to fit in RP4. I sanded off RP3 end till it was paper thin along with the the inside of RP4 and now they fit. But it took me 2 hours of measuring , sanding and fitting to make it work
So yes it can be done. I hope the 1/32 Aires f16 cans for the Tamiya don’t have the same issue