One of the stronger reported whole plant values, which is uncommonly strong when compared to average results is 0.12% fresh weight.

200g at this weight would be 240mg mesc...

Weight is far easier to make estimates about than length.

I've seen 1 foot sections weigh over 2kg (around 4-5lbs) and I have seen 1 foot sections that weigh only a few ounces... clearly thick is going to weight far more.

Some cultures used these plants for well over 3000 years, they do have specific things they do to "increase" potency. I trust that their methods are not worthless or symbolic. Essentially the plants are cut and stored in darkness for around a year...

Stressing the plants while they are growing is going to decrease growth, which decreases alkaloid content, however stressing cuttings that are not growing is practical.