Jeez, sorry I didn't see this post sooner. I have a Woods 6500 backhoe, with subframe and PTO hydraulic pump that I have hooked up to a B7300. I live in the Sierra foothills in California and have some pretty serious rock and clay in some spots. Someone made a comment about the tractor not having enough weight to dig through some stuff, and that is true but I've only had real problems trying to dig up a slope that is mostly rock. I'll probably ask my neighbor to bring his big hoe in for that.
But I'm really happy with the setup. It is a better solution (IMHO) than the Kubota setup, at least for the smaller tractors. Yours is a bit bigger than mine, but I'd still think that having the subframe would be a Good Thing. You can throw the tractor around pretty good with the hoe, and any extra strength in the frame will certainly help.
The subframe also helps by adding weight under the tractor's center of gravity. Yeah, it does get spooky on slopes, and there is a tendancy to get caught on certain terrain. However, for the smaller tractors I am convinced that is the way to go.
The way I think of my tractor with the hoe on is basically a platform for digging. The tractor can be used with the FEL (uh, make sure you have *lots* of weight up front!), but it isn't exactly nimble. But it works fantastic for lumbering up to a spot, planting the hoe, and digging.
If you have a big enough tractor, the 7500 might be a better choice - I don't think you can have too much reach when operating a hoe. Oh, and the comment about bucket size - true. Don't go bigger than 12" for hard soil, and you might even consider smaller if you have really nasty stuff. My neighbor with the big hoe runs an 8" - although it is a heck of a lot deeper than my 12".
Hope that helps. Sorry I took so long to get back to you...Chris