Please post pictures, when you complete your installation. Both of the installed spacer and finally the new stance. A before picture would be good for comparison.I appreciate the answer, but the studs are 25mm long. 15mm spacers would actually leave no room for the bolts once the wheels are on. I Feel you have misunderstood me and/or spacer measurement.
I wanted a bit more filling of arches. Lowering has pulled the wheels in a little much. I have 5mm (still allow 8 turns of the nut) and that helps. The 15mm DRM style (bolt on, hubcentric) are pretty much industry standard.
I have now confirmed the wheel recesses are 15mm. So with 15mm spacer on a 25mm studd, only 10mm protrudes. So 15mm should work fine.