This medium shredded loofah is great in CP soap, but also in Melt & Pour when you want a scrubbier wash, but not too scrubby!
I love this size in Goatsmilk Melt & Pour Soap - I personally use 1 tsp per 130g bar, but you may wish to adjust this to less or more once you have tried your soap. With Melt & Pour Soap, its easy to test by just making one cavity per trial, and with CP, just set aside enough from a larger batch to test how much loofah you would like per single bar and calculate your volume batch size from this.
We squish as much loofah into as small a bag as practicable, so do tease it apart to get a good spread through your soap.