Time to Clamp Down

The load is on the bearing not the motor. The reason is physics. The weight you are adding presses straight down directly onto the bearing. The motor on the other hand is way off to the side. The motor applies torque. Torque is a lever arm. The further from the center you add mass the greater the lever arm and the more the torque so the harder the motor has to work to turn it. Your record clamp is very small diameter, it hugs the axis of rotation. So it could be 240 ounces even, it will not be hardly any different in terms of torque. 

Also the motor really only has to work harder to accelerate this mass. Once spinning at speed the extra power is all down to bearing drag not rotational mass. This is why my turntable with lead shot filled platter at 28 lbs uses the same motor as a plain acrylic platter without lead that weighs a fraction as much. Only difference is how fast they come up to speed. Once at 33 there really is no difference in motor load even in spite of the two to three times greater mass. 

So experiment and use whichever one sounds the best, and no worries about the motor. 

The bearing too by the way should be fine. They are usually so over-engineered there will be no difference in wear just as long as the lube is there.

Thanks millercarbon....that makes total sense. I should have paid more attention in science and math classes. Good to know the laws of inertia and motion apply to something I can relate to on an everyday level.

the motor has to work harder as well just like a heavier car puts more load on the engine.

Thorens had a very heavy weight for their turntables.  I believe it was around $300.00 or so.  The Project heavy weight is around $100.00 and comes in a neat wooden box and is around 700-800 grams.  I used mine for a couple of years but now switched to the HRS weight which is a little over 380 grams.  

My clamp is 224 grams will grab any nub that protudes over the record.
I say that you have NOT exhausted all options.