Schlenk line CFM

Looking for advice on the ideal CFM or m^3/h for the vacuum pump used with a Schlenk line. Seen some afffordably priced second hand E2M0.7 edwards pumps but there data sheet says only 0.9 m3 h-1, compared to most labs i've seen using RV3 and 12 making me think it might be undersized. Thanks