If you want to be serious about shooting ARA or IR50 I will suggest using a rest. My friends and I shoot off bi-pods, basically because we shoot 25-30 local non sanctioned matches a year, that require the use of bi-pods and we go to only a few sanctioned matches during the winter, all of which are indoors.
Bi-pods do work well, as long as conditions are favorable, ie shooting at indoor matches. Outdoors you will need to pay close attention to your wind flags. Personally I cannot look through a scope and manage my wind flags at the same time, I am sure some can however. At our local matches there are no wind flags, other than a couple of ribbons hanging from the rafters of a drafty barn, that are usually going in different directions. They really play no part in the wind hold off in these matches.