i normally do:
resizing over layer options.. so all clips in this layer are sized this way. (In r3 the clip settings got overrided by that, don't know if there's an extra option in r4, don't have it right here now!)
so if it fits i normally drop my widescreen clips in an extra layer.
if i want to use the clip in an layer with 4:3 settings, u can use the fParameter Effect as a workaround and simply stretch it to 16:9
hope this helps!
there is also a max patch to resize the clips in layers (it came out before the layer resize function in r3, it was not built in in 3.0). Maybe this also fits your needs, but also i don't know if the osc adressing is still the same in r4 so that the patch runs correctly.
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