Go for it. I believe you can generally rebore the '06 barrels on the Japan 95's up to about .375. Sometimes you can get away with .411, but there is a hard spot under the front sight that is tough to recut. Not sure if your model has the brazed on front sight, but you should have no problem going to .358". This is all from my recollections of reading I have done on the topic...

If you are not afraid of going a little wild(cat). You might take a look at the Hawk cartridges. There is some info here http://www.z-hat.com/HawkContents.htm - the .375 Hawk/Scovill seems to be the most popular.