Weight, Clamp or stabilizer?

7/8" is ample for most clamps (are you allowing for thickness of the mat?) IMO, a real clamp is the way to go — some are very light, very inexpensive and very effective.

I don’t understand using a weight. I have a massive one, 800 grams, and it can’t flatten even a slightly warped LP — whereas a clamp, exerting active pressure (and weighing 90% less) does a far better job. And you are right to consider the load on the bearing.

You are "willing to tweak", and once you have the clamp, there are some very neat tricks to flatten the record totally: full contact with the platter right out to the edge. These tweaks are not expensive, and readily available: only two small parts. They require a bit of DIY but well within the skills of even a modest handyman, with basic tools.

And it really works. You’ll see and hear the improvement.

I don’t know if I’m allowed to recommend one here. If so, I will. Otherwise, you needn’t spend much, as long as the clamp has a collet. When you get it, I’ll be happy to elaborate on the tweaks, or send you links to a simple how-to.

Let us know.

The best lightweight clamp with chucking lock arround the spindle is Orsonic. The silver panel on top act like a button to open chucking lock. It's cheap

For those not overly concerned about their "audiophile cred", the Orsonic was rebadged as a Monster Cable clamp. Totally identical, but for the name — and the price: ±400 for the Orsonic, ±100 for the (ugh) Monster these days. So if you'd like to save money, and can live with the ignominy of owning the Monster brand...

I had one and it is, as Chakster says, a great clamp. And it looks great: not ornate, nor a characterless block, it looks like Saarinen might have designed it.

It is not, however, lightweight. Many clamps are far lighter, and with the collet/cluch mechanism, weight doesn't matter — except to the bearing. 

I HATE stopping and starting the turntables.

Changing LPs while the platter is spinning is not ideal practice.