Here's a piece of advice for SOI, it may have changed since early 2003, but we did very little PT (SOI West). We humped everywhere, but I think we only had three or four actual platoon/company PT sessions. One of the last events at ITB was/is a PFT, and the lack of PT showed. I graduated boot doing 22 pull ups and when I left ITB I was down to 14. I was a scrawny fucker weighing a measly 155lbs at 6'2", so that's pretty sad. On the weekends off I would go to the gym, but let's face it, that isn't nearly enough to grow, let alone maintain upper body strength. You will have time in the field to smoke and joke, so I would suggest using that time to do pack PT. The biggest complaint for any line company is boots coming from SOI not being in shape. Now think of that going from ITB to BRC.
Best of luck on your upcoming endeavor.