If you don’t fit the form securely under the free edge or you start to leave a gap between the form and free edge, this is going to create a structural weak point in your application. The product will have to run into the gap that’s been left causing a glitch that’s very easy to catch and break as it grows out. If you have a big gap underneath the free edge, this will also create a weak point and a ridge as it grows out, whilst making you have to build the free edge twice as thick to allow for the space. This will make the free edge tip heavy as it grows out possibly leading to excess lifting due to the weight as well as the possibility of breakage