I figure I should follow up in case someone finds the thread in search results.
I ended up with the Peruzzo Fox Cross 1600:
Iowa Farm Equipment -- Peruzzo Fox Cross Ditch Bank Flail Mowers
The price was unfortunately very high, and I'm hoping that it will last long enough to make it worthwhile. But it fits the tractor fine.
The difference between the two companies (VMC and IFE) was alarming. Getting anything out of VMC was like pulling teeth. I called IFE once and talked to Scott, who had all of the answers I needed. I called back a few weeks later with more questions, and we picked up right where we left off, since he had taken notes about what kind of tractor I was going to use, etc. Very impressed with the organization. The mower was in stock and shipped promptly. The skid was huge, as you can see it on my trailer that is just under 7 feet wide.
I did my own rear remote, using the Prince SV series stacking valves. There is room to put the valves behind the seat, though I did scoot over the orange safety triangle. The local tractor shop made up the hydraulic hoses to my specs. There are three hoses that run to the back of the tractor: an inlet, an outlet, and a PB. The WR Long third function valve is in series with the Prince valves. The loader valve PB goes to the Prince inlet. The prince outlet goes to the third function inlet. The third function outlet goes to the loader return, and the prince outlet joins it there with a tee fitting.

The valve body is mounted to the back of the horizontal cross piece with a scrap of 1/4" thick aluminum angle that I had sitting around. I made a small steel bracket to support the front. One challenging factor is that the horizontal cross piece does not have a rectangular cross section. If it did, I would have used the thick aluminum angle on both sides, but that was not possible without bending the angle.
There are two odd things that I cannot figure out about the mower. First, one of the hydraulic lines was inexplicably shorter than the other four. As delivered, one of the four lines wouldn't reach the rear remotes. My solution was to loosen the bolt on the block that secures the lines to the mower, and remove that shorter line from that block. You can see in the photo below that there are only three lines in the left-most block.
The other strange thing was that there was a 100 pound box of scrap on the skid, including worn out gears and bearings. Fortunately I was not paying directly for the shipping. If I had, I might have complained. But I can't figure out why on earth they would ship me a box of scrap.
I'm quite pleased with the mower's ability to cut. In this picture I was running it a little to low, but have since adjusted to a higher cutting height and it works even better.
