You may have the wrong cylinder then?
One thing I'd recommend in getting the right length is to simulate how you want your boxblade to rotate forward and aft. You need to determine how much travel the cylinder needs and what the retracted and extended lengths need to be. That is, rotate it forward to get the desired angle and measure that distance from your tractor connection to the boxblade connection. That should be the retracted length of your cylinder (or thereabouts). Then rotate the boxblade back for smoothing until you get the desired angle and measure that distance. That should be the fully extended length of the cylinder. Now, you may not get the exact retracted and extended length you desire, but you "should" be able to get one pretty close to it.
If you want the exact length, you might need to do some modification work by cutting and welding the cylinder connection to make it shorter or longer and do the same on your boxblade connection. It takes a little figuring to match up the OAL (retracted and extended and considering travel) of the cylinder and where to put the connection points, but I actually did that on my set up, so it is very close to what I want the boxblade to do now.
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