I have ED (17 years of diabetes) so I often need to pump just to get an erection. Accordingly, I usually enter the tube flaccid and hope to come out erect, or at least semi erect. After 10 minutes or so in the tube, I reach my normal pumped size (mostly packed and 1/2 inch longer than unpumped erection) which is the same weather I am erect or not erect. I only know if I was erect while in the tube, when I exit the tube and I remain erect (usually when I take Viagra). If I am soft or it goes flaccid within a few minutes after exiting, I know I wasn’t erect.
My point is that when my shaft is under vacuum, it is the same size weather it is erect or not. My question then is: If you “normal” guys loose your erection while in the tube, can you actually see a difference? I can usually feel a difference, but have never visually seen a difference.