You can get shims!
Thin Shim Flat Washer Ultra Gasket Stainless Steel Plain Adjusting Ultrathin M | eBay
SUS304 Stainless steel Flat Washer Ultrathin gasket Thin shim. Thickness=0.1mm, 0.2mm, 0.3mm, 0.5mm, 1.0mm.www.ebay.com
Maybe get some M25x30! Then you've got a nice metal ring filling the spot. Have tried it on a few watches and it looks pretty nice!
oh so this would fix it? thanks mate. i'll put this into my box of options.