If rear wheel clearance is too limiting for your use, you might consider dimpling the chainstays for a bit more tire clearance so you can easily run 25mm. Dimpling chainstays would be fairly easy and safe to do IF the chainstays are constructed from one of true-tempers CrMo non-heattreated tubes such as AVR or Versus. Search through framebuilders section for dimple instructions. True temper also made a number of heat treated tubesets such as supertherm, OXII and VHT (versus heat treated), those would be much more difficult to dimple without damage due to higher strength and more brittle metal.