Filters on Velvia 50 (Polarizer/Warming 81A)

Does anyone have any experience using a Polarizer & Warming Filter combination (i.e. Moose's Warm Polarizer) on Velvia RVP50? I will mostly use this combination on shaded landscape/scenery and was wondering if there are any odd color shifts if I used this kind of filter on an already saturated film like Velvia. Am I better off buying the two filters separately and stack them or is the combined polarizer/warming filter just as good?

I normally do 4x5 B&W landscapes but want to get back into color landscapes. I'm also not sure if the combination polarizer/warming filter have any odd effects on B&W film - so I may consider buying them separately if it does. My main landscape lens is an Super Angulon f/5.6 with an 82mm thread. I already have the Cokin Z filter holder but I am debating whether to get the screw in type or the square glass filter inserts.

I would also appreciate any filter recommendations if you have one.

Thanks in advance,
Ray

The biggest issue with velvia 50 is that it begins to shift towards magenta on longer exposures. For longer exposures, Provia is often a better choice unless the magenta shift works in your favor. I can't speak to that particular filter, but I've used combinations like 81b and GND or CPL on Velvia and the results are fine.

I have used a 81A warming filter on Velvia 50 years ago and gotten good results.

Jeff