I ordered a few Wika 28mm gauges with the plan to replace the FX gauges on my Royale and Crown. I turned them down to 26.5mm. There's not a lot of material left at 26.5mm and I found out the hard way that by trying to go a little smaller that just didn't work. At 26.5 I did have to enlarge the hole in the stock just a little. I used sand paper rolled up on a slotted 3/8" rod and chucked up in a cordless drill. I think they turned out really well and I feel very comfortable with the accuracy of the gauges. When I received the gauges I checked each one against my Crystal digital test gauge and if they weren't right on the money they might have been 2-5 bar off at the very most on the worst one. Anyway here's how they turned out.
The Royale....
The Crown.....
Jking
The Royale....
The Crown.....
Jking