In this work, we report on a series of pilot scale production trials investigating the effect of addition location, dosage velocity ratio and dilution level of a single component retention system (CPAM) on filler retention, formation and in-plane web structure uniformity for a fine paper grade. Specifically, we considered addition levels (500 g/t and 1000 g/t), dosage velocity ratios (2 and 4.5), and pre-dilution (300x and 600x) and addition location (before and after the headbox pump). The in-plane distribution of fibre and filler material in the final product was then mapped in high resolution over 10m paper samples using moveable radiation emitters and detectors.It was shown that addition of CPAM before the headbox pump resulted in a reduction in filler retention and poor formation in the final product. The addition velocity ratio was shown to have only minor influence on retention, formation and web structure variability. However, low CPAM dilution levels resulted in a high degree of variability in the distribution of filler and fibre including streakiness. Moreover, at low dilution levels, the in-plane distribution of filler was highly correlated to that of the fibres. By optimizing the dilution level and addition location, conditions could be established to reduce CPAM addition levels without adversely affecting retention or product variability.