I've been diving an SMS75 for about a year, perhaps 90 dives or so. I'm almost always using a dry suit so my situation may differ slightly. For drysuit, light undergarment, HP120's, I started with 2# on each shoulder and 2# on each waist strap. Waist mounted weight did not interfere with the tanks as I mounted them inside the D-rings on the bladder. I was a little tail heavy so I opted for the weight plate. I prefer the trim options available with the weight plate. I have had the inflator installed both up and down. My instructors who also teach backmount and rebreather encouraged me to install the inflator on the top to start even though one of their rigs has it mounted on the bottom. I notice the inflator elbow against my shoulder gearing up but it is not noticeable in the water.