Fuji Velvia and Lee Big stopper

Its been some time since I used film (E6) having converted to digital a number of years ago. Have recently purchased a Nikon F5 and will use it mainly with Fuji Velvia until Kodak bring out their new Ektachrome.

When I was shooting film previously the Lee Stopper series was not on the market and so far I have only used Big/Little stopper with my Nikon DSLR. Can anyone give me an idea of what I should look out for from their own experience of Velvia and Big/Little stopper?

I am aware of reciprocity failure and the need to allow for that with film but any other advice or comments would be welcomed.

Maybe just try it out. It's only gonna be that 1 or 2 frames out of your 1 roll.

I have shot slide film not Velvia, but Kodak Ektachrome with Hitech 4 stop ND and I got a strong magenta cast. The same as happened to a 2004 dSLR. However my 2013 dSLR does not happen. I think it has got something to do with the sensor. Yeah to me I still shoot film occasionally - so I cannot read what others say because they have only used it with a modern dSLR.

Edit - I tested this without doing long exposure ie reciprocity wasn't an issue.

Image here:

https://c1.staticflickr.com/7/6145/5939140700_93df507b11_o_d.jpg