Looks as though this is coming along well, although it's a shame, some of the issues with the earlier BR & LMS van kits appear to have been carried forward to these wagons. The metal castings seem to vary between batches, sometimes they are a sloppy fit leaving gaps and at other times they require filing. Good to know they now have the buffer spacing correct. You seem to have been lucky with the vacuum cylinder casting, many I have received have been poorly produced and I usually try and fit a replacement from an alternative supplier such as ABS (w/metal) or Parkside Dundas (plastic).
Must admit I usually don't use the white metal safety hoops, but make my own from heavy duty long staples, using one leg as supplied and bending the other as necessary. I have found that Slater's axles do fit if you deepen the holes in the axleboxes, although it has to be done very carefully to ensure you don't come through the front surface, as I know from experience.