What brand caps did you use in the power supply? It looks like TUNG brand? Cap type can make a big difference(more due to construction and good electrolyte IMO). Often if the caps are not that good with ESR you need more ufs. A good low ESR etc 1st and 2nd cap in the power supply should allow the standard values to be used. Part of the sound of the Champ is the stock values. FWIW the original 16uf might have been more like a 22uf when new. Older NOS caps I measured often could be higher in value than marked and new caps often are right on value or maybe even under value. I have measured a lot of caps over the last 20 plus years.
For fun I often reduce the values of supply caps sometime 1/2 stock value but use caps like polypros in the power supply,you often just can't drop a polypro in the first part of the power supply location without thinking and adding a part. Sometimes just enough cap ufs is all you want with a guitar amp if you want it to compress due to power supply sag.
With the champ you might even want to "adjust" the output tube cathode cap
