Thanks... once I get the exhaust off, I'll try to file it down some before putting on the homemade ones.
Here's a little tip that might help.
Clean the flange, gasket side, and paint it with a black magic marker. Find a good flat surface, glass works best, or any known flat surface and rub the flange against sand paper laid down on the glass. One or two swipes will show you immediately where the high and low spots are. File or sand until you have a flat uniform gasket sealing surface.
The mating machined gasket area on the cylinder is typically pretty flat but you can check it the same way. Use a flat object, wood or a flat file with sandpaper on it to run across the exhaust port. You can stuff some paper towel in the port so no filings get into the cylinder.
When things look good reassemble the exhaust with your new gasket and torque the nuts or Allen head cap screws down to 60 to 80 inch pounds then recheck them after the engine has reached operating temperature a couple of times.
Good luck.
Tom