BlackMagic video Out : HD fine but SD jerky

[filmsdunjour]

Hi everyone,
I've just installed a BlackMagic Intensity Pro on Pro Tools HD 8.0.3 system (macpro 2007, 2,66 4 cores).
Monitoring HD sources looks perfect (Apple ProRes 422) but SD sucks (DV or ProsRes), I see blocky images and terrible de-interleaving.
In Final Cut Pro, I have to choose the right output setting, fitting the video format I use, for the card to output video correctly.
In my case, I have to use the HDTV 1080i50 setting for HD and PAL 50 for SD and then everything's fine.
I know all DeckLinks card behave that way, so as there's no such setting in ProTools, how do you guys monitor SD video with your Decklink?
I don't want to waste my time and my disk space transcoding all my SD videos to HD, this is not suitable. Most of my SD projects are the ones I have to work on very fast...
Keeping a Canopus for SD playback is my option for now, but it's frustrating as the Decklink cards handle very well SD video... in Final Cut pro...