It depends on how much loss of quality you'll accept and still say it covers. It won't meet Schneider's MTF requirement at 8x10, which is why they say it won't cover. Their requirements are very high, though. The people I know who actually use it, including me, think it covers about 80* at f45, which gives it coverage to spare. So if you're taking regular pictures, you'll be fine. If your shooting test charts, you'll have a drop off of quality at the extreme edges. I also use a 210 g-claron on my 8x10. For what I do, it covers 8x10. The G-claron is basically a modern dagor.
The only way for you to really answer your question is to get a lens and test it. They really aren't all that expensive. If you pay shipping, I could lend you one in a barrel if you promise to treat it well and send it back promptly.
I can not say for sure, but others have tended to suggest that single coated lenses often do not produce as good color as multicoated lenses. Here is a case for someone like Kerry to step in and make some comment. They should probably be better shielded from possible flare as you mention.
Put me down for another user of the 240 f9. Plenty of coverage, small, light, wonderful lens. Don't shoot much e6 in 8x10, but if you're worried about color, you could do much worse than one of these. Just do it! tim
I've shot 8x10 color with my 240 G-Claron and it works great! I don't have any scans of that particular shot, though if you're interested, pm me here and I can see about scanning it and posting a link to it here.