Hey El, great you got your guitar back
. Maybe MikeB can chime in on this as he's done a shielding job on his strat with good results (I'm pretty sure he did ALL the cavities to get it solved).
I've not ever tried to work out which angle is more susceptible to EMF (EMI), it happens, you turn it comes and goes, you try to stay in the sweet spot.... I know fluorescent lights are a problem
, particularly with single coil PUs. The hunbucker was invented years ago when there was much less EMF pollution (3G/4G, wireless everything, bluetooth etc), the problem then was more 50/60hz mains hum. So they added a 2nd coil wound out of phase (reversed) to the single coil PUs which thus phase cancelled the mains hum. Phase cancellation works well at low frequencies, not so good at high frequencies (tends to comb filter etc....). I only came across the "stack" PUs recently, a Seymour Duncan offering, so don't know much about them, but I'd proffer they are doing the humbucking thing in a single coil size (so good for 50/60hz hum reduction ?). The shielding, if done well, should eliminate much of the EMF as you're (as far as you can) encasing it all in a fareday cage.
What PU do you have in the bridge ? why is it causing issues and not the other(s) ?