I stretched the spring by hooking one end to a heavy bolt in my work bench. Hooked the end of a ratcheting tie down strap to the other end and secured the free end of the strap to my vice. Ratchet it and opened up the spring slightly (just enough to force a washer in).
When away from home I also used the front bumper of my Jeep and trailer hitch on my m/h with the tie down strap in between the two.
Even with a bottle jack the springs had to be stretched on my m/h. The jack made the whole plate unstable and since I had to stretch it anyway I just put a few more washers in to make it long enough to simply hook into each hole.