JS & AA. Had a busy day and only just able to respond. You point out that you have a Ground Idle position at about 10 degrees throttle position and a Ground Start (with Detent) at 18 degrees.
As I said, none of the Military C130's (A-E-H) that I operated on had a Ground Start throttle position. Ground Idle is a detent position at 18 degrees, which lines up with where you reckon you have a Ground Start detent. I can't fathom why you would then have a ground idle position a further 8 degrees back toward Reverse. As a matter of interest do you start in Low Speed Ground Idle or Normal?
And yes, I also reckon the APU was a much better setup than having the GTC/ATM combo.