I tried that once with I think it was my first 372, the 372xpw (that I put a standard handle on. In case you don't remember that version, it had another cc or so, that's why I did that) and it didn't like it. Maybe you gained chain speed but she lost her grunt. I didn't run it long like that. No good. You would of had to really baby it and hold it back. That was just cutting too. For milling I could only imagine how miserable that would be. They are cheap enough to try but haha I can save you the time and the few bucks and tell you, I bet it wouldn't last a full minute on that saw until you went back to the oem rim.
I just had a 20" bar too by the way. I couldn't stand the loss of grunt and how weak she felt. It's been a long time, but if others prefer an 8 rim on the 70cc's I guess I get it, but it wasn't for me. Just not enough nuts. I couldn't stand using a powerful saw that you had to "help" cut, if you know what I mean. Best way to describe it. For milling, I don't understand how anyone would think that would be advised though. I mean, I wouldn't even bother trying, I just know how poor the results would be for you, but you're not out much to give it a go. Just don't burn your saw up. I don't think she'd like that long term.
