Origin/Rega VTA adjuster?

I have just got the Origin threaded VTA adjuster for my Planar 2 and I cannot seem to fit it.I think the hole is too small for the adjuster and without banging it in with a hammer... Should I force it in,I thought these were supposed to drop in according to Origin?.Any advice appreciated
You must file the hole open to allow the adjuster to turn easily, but to not be a "sloppy" fit. I filed mine a little at a time with a round file, and kept trying the fit of the adjuster as I went along, so that I didn't file away too much from the armhole. It should only require a small amount of increase in the diameter of the hole, and you can probably do it in about 5 minutes.
Thanks for your response Twl,I have done the filing with the sander from a bicycle kit and that seems o.k.How do I set the nut and washer under the plinth? It feels a bit wieldy,can I leave the washer off?
I don't use the toothed washer myself. As long as the nut holds okay you're fine without it.

Don't overtighten the nut BTW. Hand tight or a pinch more is plenty. I agree it's pretty unwieldy.
I also leave the washer off.