I don't know if you can run only one side but you can just run CMYK. I understand cash flow problems but you won't be saving any money, it still takes the same amount of ink per m^2. Original ink is at most 2.5% of any given job so we consider a full set of carts loaded and a full set on the shelf a mandatory inventory at any given time. We are a small shop, I'm sure others here stock dozens and dozens. I wouldn't want to run mine CMYK and loose the extra gamut.