I have not done that conversion, but it was somewhat common when Danish rolling blocks were first imported in quantity. Then reports started coming out of damaged converted guns, which some attributed to the oversize chambers on account of the difference in case head size, and others blamed on different factors, such as inferior lots of steel used in some of the barrels.
You'll want to cast your chamber to find out exactly what you have--I think there may be variations in chamber size for the original cartridge, and I know for certain there are also different 11mm Danish cartridges--differences that are not apparent to the naked eye. Also, as Sir Charles suggests, you don't want to hot-rod these guns, regardless of chambering.
If you're determined to cut the old girl, do a careful examination and some research first.