Re: Optimum barrel length for 7stw?
the standard is 26" for the STW. The 28" will add some to the load, and might help with the heavier loads.
The other question that I have is how do you plan to use the gun? Will you mainly be stand hunting with easy access or will it be a carry gun where you might be going up and down mountains with it.
For the heavy loads, either of those twists will work, just work slowly with the loads with them.