Don't do it. There is a 40% reduction in flow.How about reducing fx5 (25mm i think) pipe to 16/22, would that cause problems other than reduced flow?
And you will have the same problems with flow reduction. It doesn't matter where the reduction occurs. Using original outlet tube makes no difference if there is a reduction in the cross sectional area at any point in the flow circuit.I had the same dilema. Reduced only intake to accommodate atomizer and inline heater. Outflow is with original hose.