2) I’ll go with ‘how sure am I’ as I can’t tell for sure, I’m following the generalised principle that we reach 39-43C after 10 minutes, however I’m using my hand as a backing medium when clamping and my leg whilst doing bundled stretches.
I can definitely feel the heat progress as my workout continues, however I feel it cool very quickly. I never feel much heat on superficial skin unless that part of skin is in contact with the transducer and even then, the gel is normally cold so I don’t feel it much. I was thinking of establishing a high room temperature to prevent heat energy transfer from penis to air and therefore reduce rapid cooling so more of the penis would stay beyond 39-43C.
There have been conducted temperature trials with a 3MHz US-apparatus with an intensity up to 2.5W/cm2 to understand the temperature correlation between dorsal and urethral temperatures.
I would highly recommend that you are tracking the temperatures during your test as we can see peaks above the proposed “safe temperatures” with such an intensity in well under 10 minutes..
Even better, follow Igigi by example and track every detail of your work so that it could help forum members going forward.