I have not experience with testicular germ cells isolation but I have used Ficoll for stem cells. I used 435g for 30 minutes. That should distribute cells in different layers. Than carefully test every layer. You should get in one layer what you are looking. You can begin with this speed. You need to calculate rpm for that 435g in your centrifuge. I used 15 ml tubes, that should be ok for 3/4 testis.

Good luck

BTW, once I worked in AIIMS in Reproductive Biology as a pool office

@Subhash C. Juneja Good to know you from the same department sir.