welding leads for dynasty 200 and shopmaster 300

[H2o]

I did a quick sketch of my shop and adjacent area, where I would be stick welding. I don't think I would need anything longer than 75'. So 4/0 might be overkill.

[H2o]

I have a dynasty 200 and shopmaster 300. I want to set up the shopmaster to do stick welding. Machine came with two 2/0 runs of 25' wire. I wanted to set up some quick connectors at machine so that I could swap cables between dynasty and shopmaster. Since shopmaster is the higher amp machine, I am calculating on that one.

I have been stick welding on the dynasty in the past, with the miller contractor package leads (#1 or #2, with 15' leads, I forget). So never had to think too much about welding distance.

Question 1, looking at the Weld Output Terminals and Selecting Cable Sizes chart in the manual, it gives "Total Cable length in Weld Circuit not exceeding" numbers. So if I am welding 100ft away from machine, I would need to calculate for 200ft weld circuit (from machine, to where i am welding, and back to machine)? Is that correct?

Question 2, I have read that you can use lighter gauge where you are working to avoid lifting all that additional weight. Is there a rule of thumb there?

I don't know that I would need much more than 300amps. I was looking to go with 4/0 wire as it would give me some additional flexibility and the cost is not that much more than the 2/0 wire.

Thanks.