Gunmakers set-up looks top notch, as well. Great "action" pic!
Northstar, reagrding your issue with frame mounting and stresses:
What I have learned reading and by observation is that the larger the blade, and the more work it is doing, And the stronger the machine, the more beefing up needs to be done.
As KennyD points out, for snow, if you are using a spring-tripper then you won't have those sudden impact shocks from suddenly hitting a curb, fire hydrant or lip of a ManHole cover. Those are the shock loads that bend metal.
In snowy conditions, under normal plowing, CUTs and SCUTs are going to lose traction way before they bend frames.
I appreciate your concern, and even respect your idea about trying to connect to the FEL mounting point. Would it be strong? heck yes it would.
Is it necessary, perhaps not.
Look at Dirt Dozing for a moment. Now there is a case where , with the blade locked rigid, and cutting into vrigin soil, with good traction, you would be putting some real load onto the connection points.
I don't know a whole lot about Deere's set-up on their front hitch systems, so I will defer to the experts, but, I would suggest you poking around their website, even going to a showroom, and check out how they connect their front hitches.
I'm not so worried about constant plowing loads on my machine, and new blade set-up for several reasons: I am primarily going to use it for snow, or loose material. My machine is going to "break traction" (slip) far before I break anything metal.
I'm not trying to tell you to build something flimsy, but think it through, and take a look at what the factory does.
Hope this helps.