Best thing about templates is they keep you out of trouble !! It makes it far easier to keep thing symetrical. Plus you don't have to read up on the hows and whys of porting and two strokes in general, although you'll need the knowledge to go further. This especially true when it comes to raising/modifying the exhaust port. (more to follow)
In reality, it wouldn't surprise me if someone doing dozens of port jobs a year didn't use a template, poor man's CNC.
Welding on Banshee cranks is done to keep them in phase, exactly 180* of difference in stroke,.
But, then again, there are some Banshee owners that think the Niche cylinders are OK .........
When modifying the exhaust port, AVOID making the roof flat, a nice arc/radius is better. While a flat roof delivers a more "concentrated" hit of the powerband, but is extremely hard on the rings.
I'm actually going to be De-tuning/ re-tuning my Blaster, might have raised the exhaust a bit to much. Then adding a 3mil crank raised it more with the spacer plate. My plan is to do a little measuring with a degree to see if I gain enough when removing the plate to justifiey having a a custom head cut. Not that there's anything wrong with the way the powerband is, it's that I'm getting old and slowing down a bit