Just as an update;
I did a couple of trips this weekend to try things out.
I brought my newly acquired Mamiya RZ67 with me, along with a 50mm f4.5 (Mamiya??) lens.
This lens has 77mm filter threads, so the cokin-p fitted and screwed in nicely, no problems at all there =)
Now for the metering, I used both my Sekonic l-358 and the Sekonic l-208, which came in the bag when I bought the camera used.
I used the 40 degree lens on the 358, but still, with the sun in my face and all, short on time and kind of stressed, I actually ended up using my 1ds mk II's spot to get a few readings around the lighter areas of the scene, as well as measuring the mid tones to get an idea of the contrast.
Still, calculating 5 added stops, due to pola + nd-grads, was kind of tough there and then, so I bulb-exposed from 5 to 25 seconds (light was fading fast as well). Most shots were fine around 10-15 seconds at f16.
Going to take a look at a few of those meters that swhiser mentioned, because I simply don't trust a reflected 30-40 degree measurement, made with the sun directly in my face....thinking that the sunlight must somehow get scattered into the light metering sensor somehow, because they are so exposed...I don't know, a lot to learn i guess
Here's the sea-scape shot I am talking about:
The next image, was measured using only the seconic l-208's 30 degree reflected meter. Here I simply just measured the scene in the middle of the photo and guestimated the sky-balance to be around 2-3 stops (At this pont, I am happy, as long as I get details in there, perfection comes later). Problem was that the meter varied 1-2 stops from measurement to measurement, so it seems like the sun "polluted" the readings a few times.
I did shoot some Velvia frames from the sea-scape scene, will be putting it up later after I get it back from the lab and have finished scanning
Thanks for all the feedback so far =)