Let's mandate that the ratio of flag officers/Navy ships be capped at 1/4. It seems to me that four ships per admiral is reasonable. /S
The number of admirals is not really a function of the number of ships. The number of admirals is rather a function of the executive management structure. certain jobs require certain pay grades to be in line with DOD civilian and private pay.
There can be some argument as to the fact there are unnecessary slots and if a Captain can function where there might be admiral creep, but that is different.