I think it's largely dependent on the rig. Racing boats tend to have higher aspect rigs (taller masts) and lighter weight mast sections, so the stay-sail stay needs a back stay to prevent mast pumping in lively conditions. Our CR's have lower aspect rigs and at least on our boat, the Isomat mast section seems fairly stout, so we can get away with less ideal angles on the standing or running backs. We have standing backs on our 38 and the angle is very small. I don't worry about it. I was offshore on passage on a CR 42 in some really "puckering" weather. Under triple reefed main and staysail. Somehow we forgot to put out the running back, and we noticed no issues. When we finally did put out the running back, we did not notice any difference. Based on those observations, I'd guess the rig is sufficiently stout to handle things as is. We have a Bayfield 32 also cutter rigged and also an Isomat mast section. There are no running *or* standing backstays on that boat. Lots of those boats sailing offshore with no issues.
Hope it helps,
-Tom
S/V Eclipse
CR38 #115
Rock Hall, MD