I had to chime in here,
I too have a sub compact--JD 2305 and I have owned a middlebuster for about a year. In the past, I have had issues with ground clearence with implements such as my LX4 rough cutter and my 5' grader blade. Like many others, I thought about trying to get/adapt a shorter top link, but I actually solve ALL of my 3pt clearence issues with the lower links.
Before I purchased the middle buster, I had purchased a set of Pat's Easy Change adaptors. Not only do they make adding and removing 3pt impleents much easier, but they effectively lengthen the lower arms by about 4 inches. This sounds trivial, but the overall effect on the top link is that the top link now acts as though is were shorter than it is and thus really lifts the implements off of the ground. I find that I have several inches of clearance with mu subsoiler when I crank the top link all the way back. In fact, all of my implements are now easily off the ground as opposed to before.
I did not but the Pats Easy Change for ground clearance, but it has been a pleasant surprise. In addition, the middle buster is one AWSOME tillage tool once one gets acquainted with it. After I learned how to dial in just the right angle with the top link, the MB would sink deeply into our hard clay here in Southern Illinois. After the MB dropped to the point that the link arms were nearly dragging on the ground, I adjusted the link again and the MB pulled the rear tires firmly to the ground. The traction was AWSOME, no weight could ever match that MB. After I ended my run, I lifted the MB from the ground and just looked at how much hard clay had been pulverized from deep below. I repeated this twice more, once to each side of the orriginal line, then use the loader to lift out the newly loosened soil. When I was done I had a trench 4' wide and about 15 inches deep. I repeated by going another round right down the middle of the trench and then scoopin out with the loader. Finally I had a trench 30' long, 4' wide and about 2' deep--right up to the top of my read tires. I then filled the trench with lots of various grass clippings and other organic matter to permanently loosen the soil. Finally, I pushed the orriginal soil back on to the trench which by now actually mounds higher than the ground around. Again, awsome work with one simple and relatively cheap implement.
I hope this can help you, good luck
SI 2305
JD 2305
LX4 rough cutter
LandPride 60" 3 pt finish mower
5' grader blade
loader
middle buster
Pat's easy Change