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Requirements given by large scale physics experiments and applications in border security monitoring prompted to upgrade existing large 75 mm and 130 mm diameter PMTs towards better timing properties. First, the existing dynode structure of XP4312 was improved by inserting a screening grid in front of the anode, following that applied to the XP20D0. The performance of the new XP43D2 photomultiplier was studied in comparison to XP4312 PMT. The time jitter of the new PMT was measured using a fast light pulser based on an XP22 light emitting diode. The timing properties in coincidence experiments were measured with large NaI(Tl) and plastic scintillators for 60Co and 22Na gamma rays and discussed in terms of the measured photoelectron numbers.