When I plumb a ridgid shop vac with a 1-7/8" hose size to the 1F 2-1/2" dust shoe. where is the best location for the hose size reduction that will result with the less amount of CFM loss? My gut says to do it on the discharge side of the dust deputy, assuming that I install one. thanks in advance for the input.
In general, you want to shrink the opening down at the last possible minute - keep as big of a hose as you can for as long as you can.
A larger hose is more efficient at allowing stuff through than a smaller hose, is the non-technical reason why.