Fully agree. That's why I've been pushing people toward lo pro to make use of existing 50-70cc saws. Just doesn't seem it will work out with yours without a lot of tweaking. Even the 455 Rancher I'm trying to adapt I'm wondering if it's worth the bother now. The Stihl (12mm) to Rancher (8mm) bar adapter is not that common and had to spend $20 ordering it from New England Pine (there's a cheaper one on Ebay but distrustful of quality). The lo pro rim sprockets I have don't fit the Rancher it turns out - they're for 60+cc saws as I thought. So have to order the small spline lo pro rim sprocket from Chainsawbars. As far as the G777 mill and the tricky 20" solid bar requirement, I think ultimately it's worth the hassle of getting a setup that works with it. It's just so light with a 50-60cc saw it's a joy to work with compared to a standard Alaskan mill and big saw, especially when resawing for lumber.
A lot of the clone owners crow that their saw paid for itself in a short time so no matter if it's disposable or doesn't last, they only have a few hundred dollars in it. I spent $400 on my first Stihl 87cc milling saw second hand, I'd never dream of spending $1000-2000 on a saw as a newbie, so I get that new big brand saws are only a viable choice for serious pros. But I'm a serious re-use, re-cycle, make existing things last forever kinda guy, so I like second hand name saws I can trust that will always retain value. You've got the right approach - mill some with what you have, see if you're hooked on the milling thing before you upgrade a bit more.