When I was using an X45 I clamped a long board that extended well under the desk and was as wide as the X45 base, using some rather large c clamps, to the desk. Then used 6 (3 each connected to each other) plastic wire ties to hold the X45 base to the board. I set up the throttle on a tall speaker set next to my chair and away I went.
Not sure if that will work very well with your desk however. As the clamps left marks on the formica and steel desk top
Mine is old but basically it's a junk office desk.
My CH set up is so much better IMHO
no plastic wire ties needed and only one c clamp keeps the board attached now
I have since become a sold on CH products person.