Well l filed the slide, easy, no problems, l actually filed-off more than the engine ended-up needing (made it too rich at 1/8th throttle), so l just filed the cutaway a bit to bring it back :-)
The slide (that now travels downward further) didn't touch the needle-jet (NJ) shroud, but l flatened the angle on the bottom of a 7mm drill-bit and gave the underside of the slide a recess for more clearance from the NJ, just incase l find, at some time in the future, that l have to run the slide lower at idle.
One thing to keep in mind, as the slide centre (the bit that holds the needle) sits lower (equal to the amount you file-off), the needle will sit lower into the NJ, l had to change the clip position from groove 3 to groove 5 (bottom groove) to keep things equal. Should l ever need to raise the needle further in the future, l'll just put a shim-washer under the clip :-)
My filing may (yes it was) have been a little uneven at first and my idling rpm was all over the place, a few strokes on some course emery-paper to get it square, got things right and she runs so sweet now.
So there you go, don't be afraid to experiment :-D