Adding a FX loop to a MM RD 50

Hi, have a FX loop module lyin around that did not fit into a homebrew amp. Its made for tube amps, allthough its FET Powered: https://www.tubetown.net/ttstore/en/kit-seriel-fx-loop-lnd150.html

I would like to put this into my RD50. I figured out, that the best place  would be somewhere at R42. The reverb circuit is placed there as well.

Where would the experts place it?

Should i break the circuit there or just attach it?

Any opinion on this is highly appreciated, Thank You in Advance.

I will attach the schematic, Thanks Dirk