This paper deals with kinetically enhanced copper vapour lasers (KE-CVL) performance at elevated specific input powers by investigating three laser tubes of decreasing internal diameter for constant input power (7-9 kW).To enable direct observation of the effects of increased specific input power, the three laser tubes were investigated with other parameters held essentially constant viz. the end-housings, gas handling system, resonator optics and excitation circuit. The highest output power of 104 W was obtained for the largest tube investigated, which was 32 mm×1m long.