I understand that installing a weapon attachment requires 100 credits, the modification itself, a toolkit and a hard mechanics check.
What i cannnot find rules on is how to pay for or choose the modification options. It seems for things like a filed front sight, (on which i would argue that you shouldnt have to pay the 100 credits to do as the required item is something already in your toolkit) the base mod of making it draw faster makes sense. However its obvious that the modification option with that of "smoothed frame" is very much optional. I cannot find a reference to what it takes to get said modification and am even further confused by mods that have multiple options like the marksman barrel.
can someone please elaborate?