Hi MF. I used a bog standard medium coarse file with rounded/flat sides and about 3/4 inch across, but I also had a fine needle file to do a little touching up. Job took about 1.5 hours because I went kinda gentle with it, but I imagine it could be done in a half hour. I just finished painting her up this morning (Rustoleum Painter's Touch Ultimate flat black primer) so here's a shot of the finished piece:
I left the ends of the vanes a little wide for structural integrity.
Had the scope out again last night and am genuinely amazed at the performance upgrade this produces. Delta Cygni (mag 3) at 175x in good seeing is just the airy disk and first diffraction ring - nothing else there except black space. Gone is the scatter and diffraction "swirls". Prior to this mod I needed 175x to split Izar, but it now splits at 127x. The Pleiades no longer have an artificial Merope nebula - just the stars, and Saturn no longer has a glowing atmosphere.
Thick curved spider vanes should not be used in a telescope. Straight thick ones are ok as you just get spikes not a haze of scatter. This is a game changing mod, but it's a big-boy mod so if you do it:
Put alignment marks on the OTA and front end so you know where to thread it back,
Tape over the secondary holder very well with masking tape,
Don't apply tons of force, let the file do the work.