I own two P9/RB1000 TTs. All installations have been performed "in situ", as you put it. One arm is mated with a Rega Apheta; the other with an Ortofon Jubilee. Both installations went well - - - no problems. Personally, I would be hesitant to remove the arm for cartridge installation - - unnecessarily complicates matters and poses a risk of damage to the arm.