I tried some aftermarket panels - took one look and realised they just weren't going to work. I dug deep into my pockets and bought a couple of body cut arches that were off a dry state bus and they went in like a dream - good solid metal and a perfect fit - really neat door gap and profile. Mine even happened to be the same colour as my bus : )
Part of the beauty of a body cut repair is they invariably come with surplus material round the edges where they were chopped so you can decide what to remove / save - un-pick the spot welds etc.
Eg the front arches will probably come with a bit of the B pillar so you can get a neat nice seam, they'll probably have that little sticky out seam at the front corner too.
I guess at the end of the day it's different strokes for different folks. Body cuts aren't cheap but patience is, so if you can do the work yourself and want to save a few quid you can modify aftermarket items and get the result you want.