I have found that if I need to reshape the front hairline. recession, temples or sideburns of my full caps best results are had if I do it with the cap lightly attached with tape on my head, using two mirrors and small manicure sissors. That way I can very carefully craft it to exactly how I want it to look. The problem with cutting it off the head, with a full cap at least, is that it can look different to how you want it to look when you re-attach.