There's a bit of upper body structural work in the program already (TGU and push ups, etc.) I'd say its a bit counter productive. You have to consider the task at hand and the purpose of the program. The task is running 26.2 miles. The purpose of the program is to get faster and increase aerobic capacity. Upper body training doesn't really help either of those two things. Any upper body mass that you carry becomes a burden. If you want to be fast - do the program as specified. If you're looking for general fitness, do the Foundation programs. If you want to run a fast marathon - do the marathon program. If you want to be generally fit and run a marathon for kicks, the do the Foundation programming. I think you need to reconsider your goals and start from an honest place.