ETRSi / Metz 45CL4 TTL-OTF accuracy

I have just acquired the SCA adaptor to allow TTL-OTF with the Bronica
ETRSi/Metz 45CL4 setup. I want to use it this week to do a family
gathering and have read about the impact of accuracy metering off the
film as a result of different reflectivities of the films that could
be used. I don't really have the opportunity to do proper testing and
am asking if anyone can comment.
Location will be a large covered verandah with plenty of natural light
from 3 sides (a wide river on two of these).
I was considering using Fuji NPS or NPC 160 print film. I have found
NPC to be more contrasty than NPS. Suggestions as to Kodak 160 speed
possibilities welcome. Gathering I'll be doing would require results
similar to that of a wedding I suppose, being mainly individuals/group
shots.
I am particularly interested to hear from anyone using this equipment
combination as to any exposure compensation they have found necessary.
I'm not a pro, and would like to ensure I end up with reasonable
shots. Alternative is to shoot with Metz on Auto and leave the SCA
for another time .... Thanks, Alan

Yes, the OTF metering systems can be fooled by transparency vs. color negative
film. The film's reflectivity is generally brighter for one type of film than
the other. Even though brand to brand the actual reflectivity varies, as a
class everyone's color neg emulsions are darker than their color slide
emulsions. Having used the ETRSi with Metz 45CL4 for many weddings, I have
never compensated for the reflectivity of color neg. I cannot say if you need
to compensate for the reflectivity of color slide, since I have never shot
color slide film with the OTF flash. But I would guess that the color slide
brighter reflectivity should be compensated, as looking at color negs they
never looked to be overexposed.

--wilt