[Silent Street]

I would not be concerned at all if only negative film is being used. Transparency film though is much more sensitive to faults in shutter timing or apertures, with as little as 0.3 stop quite noticeable, 0.6 stop almost a fail and 1 stop, out of the question. The speed gain seems insignificant to me, with all Pentax 67 / 6x7 bodies having 0.5 stop values. If it really does matter, change to a different film speed using the ISO dial.