Ed, No it will still perform as a CAT but does give you extra margin on the fuel front - you should not however plan to use the CAT fuel in general but it is an emergency. The CAT sizes are also designed to supply around 30 seconds of fuel supply at full throttle (dependant on turbine naturally) before they reach a point where the air starts to get drawn into fuel supply.
The bores on the CAT fittings are designed to be large to avoid restrictions and resulting cavitation problems, warming the fuel tube at the end and pre-stretching it a little by pushing the end of a pencil in it while warm will evenly enlarge the end enough to go over the barbs. 8mm OD Tygon fits without warming as a note.
marcs