I think it might be too much stress. From the pivot point to the bag you would have to make it sooooo beefy that it would weigh a ton and still put alot of stress on it. I could be wrong but deffinately would work. Late
it will werk fine, just like everyone else said, just keep it beefy. I'm warning you tho, you do not want to run your top bars from the rear, your pinion will be a complete bitch and you will replace universal joints like crazy. i speak from having a setup similar to that for two years. The canti will werk fine tho. It won't create any more stress than a front bag would get w/ the engine over it.
I agree with the responses here. The one thing you will want to do is make sure you make the distance to the bag from the pivot point equal to about 1/2 the distance from the pivot to the axle. You do not want to overload the bags.
You might get huge lift if you keep the bags super close, but it is really pointless. You will get big lift, but the bags will be overloaded, you will have pinion problems and you will never match the lift in the front.
Lastly... listen to all these guys when they tell you to run ALL of your bars forward. Doing anything else will be nothing but a headache for you in the long run.