ok, I hope this makes sense:
first, here's the stock axle arc (at stock ride height, at the bump stop, and fully compressed - using the 1.5" data above). 298mm is the ground clearance to the bottom of the factory pivot mount on stock-sized (tiny) tires, btw...
and here's the 50mm down/25mm forward bracket overlaid on that graphic - to show the new axle arc. as before, the circles represent the axle at ride height (assuming a 50mm lift), at the bump stop, and fully compressing the bump. the relative ground clearance to the bottom of the pivot mount hasn't substantively changed. (298 vs. 303 without changing the tire diameter)
and here's a close up of the actual axle shift in the wheel well (or away from the firewall) - again, at ride height, at the bump stop, and under full compression:
at ride height, the axle is shifted 25mm forward (I like aggressive approach angles). at full bump, the axle is just 16mm forward - I'm assuming everyone is running a larger diameter tire if they're getting full compression on the bump stops, right? (why not have a little extra room)
so, I could have cheated it back about 1/2 inch, but I wanted room for tire diameter growth.

likewise, since the axle is already arcing rearward as it gets higher than the pivot, dropping the rear mount straight down would create a situation where the axle would be closer to the firewall at full bump - not ideal, IMO.
- and this is irrespective of the climbing behavior of lots of antidive, which this type of suspension has already, stock. I'm weird about unloading the front end when headed north...