Beg to differ. As previously stated, I owned an IM-602 for years. Following your recommended configuration will result in irreparable damage to the toplink threads and exert unintended stress (pushing) on the straps. It's that pushing action that bends them - they're only intended to pull. And the thread damage will occur every time the tail wheel rises high enough for the threads to make contact with the pin.
Yes, if you mount it upside down (from my perspective) the metal cross piece performs a lift function. But in doing so you subject the toplink and straps to unnecessary stress and damage. Mounted on the tractor end as I describe, that cross piece merely keeps the pinned bars parallel. Maybe it would become more clear if you equate it to the U-type FTLs. Except on the U-type, the part that keeps the side bars parallel is on the implement end. In the end, the design intent is strictly to keep the bars parallel, not to lift
The mounting method I describe (vertical while mowing) permits the FTL to swing an unimpeded 90 degree arc (45 degree forward and 45 degree rearward) in sync with the rise and fall of the tail wheel. At no time will the threads of the toplink touch metal, and there is no pushing force on the straps. When the mowing is finished, the toplink is shortened so that the FTL is horizontal. That permits the mower to be raised higher off the ground for transport, and exerts the intended pulling force on the straps.
That said, it's important that the toplink be sized appropriately to the tractor-mower combination. One that's too long will be problematic in getting the FTL horizontal for transport. One that's too short will be problematic in getting the FTL vertical for mowing.
//greg//