They are adjustable from the factor with the turnbuckles, and several folks swap the turnbuckles for telescoping arms. I believe the B2400 series arms match perfectly.
I haven't done this yet but it's on my to do list.
The B2910 has telescoping lower arms. They do help sometimes, but what works the best is to have your attachments mounted on dollies, and have everything on a concrete floor. I don't know how the size of the arms on a B2910 compare to the ones on your tractor, but you might go to a dealer and check them out.