Rather than start a new thread for the same problem I too have this problem. I have a BX25d and when I fit the tiller up to the 3pt I only have a few inches left between the joints on each end. The photo is not real clear but I only have 4 inches of plastic sleeve between each hub. If I take off the plastic sleeve I might have enough shaft to still allow sliding and sufficient engagement.
With the implement at the most extreme down location on the three point, and PTO the most level [shortest PTO length], (Put blocks under the tires if tiller need to go go lower to get the PTO level), then mark the length between the shield bells, now lift the three point up and mark that distance.
Remove both sides and lay on bench measure how much depth you can get out of the inside shaft and 1/2" min extra and what depth you need to put in if the depth is not deep enough you will need to add a quick hitch to move the implement back to get the proper depth.
You need at least 1/2 the length of the shaft engaged all the time or you will have problems.
Yes you will cut it down, but you cut both sides down, and if you notice the PTO shield is cut different than the metal shafts, copy the length it is now, for proper over lap.