I read your other thread, as well as this one ....
Why could you not ` use` the front hairline of the system? All systems [stock and custom] have graduated-density front hairlines by default, unless , in the case of a custom-made, you specify non-graduated.
If when trimming a system`s base, you should never trim /interfere with the front hairline, if at all possible......trim the sides/ back, only......cutting lace from the front means you are going ` back` into the denser hair, and this will not give a natural look, in most cases.The front area [most visible] will normally have the knots bleached /invisible, therefore, removing /cutting off sections of lace there, means you lose the best-bleached knots.
To thin-out a lace system, tweezers is not advisable..the hairs are tied in knots..trying to pull out the hairs will result in them simply snapping off, leaving the knot intact.
Using things such as Nair, is more practical, but in my experience, you need to take time and be patient..remember too, that not all hair will shed-out immediately ..so don`t go overboard when using it initially....more hairs will shed out over the next day or two when brushing the hair.
This video should help https://www.youtube.com/watch?v=rPULkcyVD2Y
If I were you, I`d consider ordering a new system and this time, don`t cut the front area ` across` .....if you need to re-shape it to suit your ` look`, you can trim the sides and back of the lace......use a very sharp blade [a hobby /craft knife is ideal] and draw the tip of the blade across the lace....don`t push it down through it....you only want to separate one section of lace from another..don`t cut the hair under the lace, and do NOT under any circumstances use a scissors. You can also purchase a thinning-scissors..this is useful for doing a ` light` thin-out....bear in mind that this cuts hair ..it will simply shorten the hair strands...it will leave ` stubble` [shortened hair/s with knot still intact ] but it helps to ` soften ` the overall look by making it a bit thinner....hope that makes sense.