Clamping for me has been an effective PE tool. My mid-shaft girth started at 4.75 and currently is 5.1-5.25. My base girth started at 5 inches and now is over 6. Much of this base increase however I feel is due to the BIB. While clamped my mid-shaft measurement is 5 10/16th.
My recommendation is to measure while clamped. I believe there are two things that occur during clamping that cause gains. The first is the overall penis expansion that occurs while in the clamp. The second is the additional expansion that occurs along where the clamp is placed. There are many alternatives to create the second variable up and down the shaft. Squeezes, additional clamps, or other techniques can be effective.
Here is what I feel. The goal of clamping is to increase the maximum girth along a specific area of the penis. For this reason it is helpful to take more than one measurement. Even if one is taken however this should be sufficient.
The bottom line is, if I am seeing the maximum amount I clamp to increasing, I know gains will come. This is in 1/16 steps but it is growth. Once a new record is being achieved while in the clamp, progress will follow.
In saying this, please note the most important thing for me in PE is not getting injured. No one can monitor our bodies reactions and comfort but ourselves. I have hung heavy weights with the BIB, and clamped to what many would consider extreme. To me, I have never pushed my penis past what it could recover from in my 2 years of PE. So, safety first is my recommendation.
I am still learning much about clamping as time goes on. Personally a heat lamp helps my expansion and I would recommend this.
3/07 7.75 bpfsl, 4 12/16 midshaft EG
5/08 9.0 bpfsl, 5 10/16 midshaft EG clamped
7/09 8 4/16 BPEL, 6 midshaft EG clamped