On the Basic tab you find a parameter "spiel" which is set to 0.15 - this is the clearance so raising this to 0.25 will give more room. The length of the spring is not affected by this (and is already bigger than the available space) the diameter of the holes for the spring are bigger to ensure that even with .3 layer this is working proper and more clearance here is needed to insert the spring. One without marking is also within the download "stl" section.