I do not think that IPUMS has the correct variables for weighting these surveys. For example for the basic monthly surveys, what is apparently needed is
CPS (Basic) Weighting Variables: PWCMPWGT Jan 1994 - current Weight-composited final weight
These weights do not appear to be in IPUMS-CPS. Thus WTFINL (the IPUMS final weight) for the basic monthly surveys) is not the same as PWCMPWGT. Nor does WTSUPP yield the right results for the March surveys.