Dwayne, I don't move the entire wall. I like to make the walls more rounded than straight.
I use a 3/8 burr and tighten up the corner radius at the pinch. I also will lower the floor there and make it rounded.
When I'm done the s/t is lower and radiused more.
I also sleeve the bolt hole that has oil in it, so that wall is pretty thin at the bolt hole.
I also reshape the roof as it transitions to the backside of the bowl. And I widen the bowl at the roof so there is some taper from the roof to the seat.
I know some guys will not open up the chamber to help the port hang on, but I don't think this is productive to making power. I haven't done any testing like that though, so I cannot say it with full conviction.
I wouldn't worry about the port past .650 lift unless it's a serious engine that will rev past 7500rpm or going on a stout 4" sb.
If you can, bolt a good intake on it and flow it that way. It usually makes the port hold on to well over .700 lift. But I believe that when fuel is in the air stream, it can easily seperate from the air if the air has to do alot of slowing down-speeding up or has to turn abruptly.
Brian