It does really help to have two, especially if you can fit both wings at the same time. You will probably need to adjust the size of your aileron travel stops numerous times. It is much easier to do this and to make sure that both ailerons have identical/very close up-down travel if you can lock both in position at the same time. They only cost $3.00 or something like that from Van's, so I just ordered an extra one.
BTW, don't spend too much time trying to align your ailerons now. You'll have the bolts in and out of the belcranks and controls so often when fitting your wings and control systems that you'd might as well just wait.
Hope this helps. Good luck.