Filter Question 1: Shift Field - when to shift it?

Question

And by "shift it", I'm really asking in what order to place it, relative to any other filters being applied. And is there a rule of thumb for this particular filter being first or last in the stack?
The Specific Issue:
I notice FCP applies the filter automatically when I add HD material to a standard def Timeline (see "Workflow" description below), where the extra material has a different "Field Dominance" than the main footage. This triggers a green render bar, which thankfully doesn't take long to process.
But I'm starting to see some odd behavior when I then add other filters to one of these clips whose Fields have been automatically Shifted by FCP.
Specifically, I've been testing MagicBullet's "Noise Reducer" filter on a few of these clips (ones where I've had to magnify the image more than it really wants to be), and once the absurdly long render finally finishes*, the playback of just these clips gets very wonky on my external monitor (with a flashing blue that eventually takes over the whole screen, but only for these clips -- and FinalCut's telling me there's nothing left to render).
* and this is the subject of a whole 'nother filters-related question I've posted in this same forum
Interestingly, when I drag the Shift Fields filter from its default top-of-the-stack position in the Viewer down to the bottom, so that it comes after the MB Noise Reducer -- and then wait for another huge render to finish -- now everything seems to play back fine.
Both filters (FCP's Shift Fields and MB's Noise Reducer) are configured in their default settings, and this apparent conflict with the Shift Fields filter appears to not occur in relation to any other filters I've also been testing (such as Sharpen and Deflicker).
So -- is this just one of these trial-and-error things, where you keep reordering the filters till they seem happy, or is there a reason why the automatically applied Shift Fields filter should always be last in the stack (even though intuitively it feels like something which should be applied first)?
Any insights appreciated.
Thanks,
John B.
Toronto
*Workflow Description*
(which might be of interest to other one-man-band, tight-budget videographers)
+I'm currently cutting a series of videos done for a local theatre company. My A-cam is a Sony MiniDV shooting 4:3, and my Timeline is the basic NTSC-DV easy setup. I generally also set up a B-cam at a different angle, which is locked off to get a static shot of the full performing area. This camera is a compact AVCHD unit, shooting at full 1920x1080. I put its material on a separate video track, and when I need to cut to it I use the Motion tab to frame the shot, resize it, and crop in as desired. Sometimes I'll even keyframe a pan and/or slight zoom to give the effect of a human cameraperson following the action live. Since both cameras are recording continuously, I only have to sync up the two tracks once -- and the end product gives a reasonably convincing impression of a two-person shoot.+

Answer 1

Clearly I need to check in with the Jolly Red Giant himself, since I'm wondering if he's the one I should be pointing my finger at with regard to a bizarre issue I'm encountering: trying to export a previously harmless sequence which now contains clips with two Red Giant / Magic Bullet filters -- all fully rendered, but the Export time is expanding faster than a Supernova.
Thread is called "Renders Gone Wild", if you have any advice on what I should do.
Thanks,
jb