Getting into the right position takes some time to figure out, and while doing that, one or more of the men may become less hard, particularly if they are a bit uncomfortable about being that close to another man’s genitals. In those cases, I was reluctant to make it a mechanistic job to get them hard again for the purposes of continuing to try and kind of force the issue rather than just going with the flow. Adequate length has been a factor at times too. It works better with guys who are bit longer than average because of the angles. Having a well endowed, bi-sexual, 32 year old who had done this before seemed to be the magic combo — at least for us.