Interesting question. I also solo and do tech dives. (by definition) I have just recieved my first tech cert and have no solo cert. I have no fear of the dark, deco or going deep. I exercize what i consider prudent caution when diving. i normally physically dive with a buddy (by definition) but realize that unless tied to the hip a buddy is not a life insurance policy. I thik all policies of that nature must be attached to me. so Whether i am alone or with a buddy my backup's are less than a few seconds and arms legnth away. If i cant meet that criteria, i dont get wet. so When physically solo i limit my self to say no overhead hard or soft, no unfamiliar water, no exploring, no current, no penitration. Depending on the situation diving solo is insane. expecially if not properly equiped. In short i solo in the recreational relm with additional limitations placed on my self. Possibly the only time i may mix tech and solo is if i had a deco requirement which is really unusual.