So from a GS perspective, are you saying playing 48min is better than 70min? Will your game GS goes down or up playing 48min vs 70min? If I remember correctly, I have played my guys in the 70ish range and didn't see much negative impact on GS. I don't know about 48min since I rarely have guys at around 48min (either way below 48 or >60).
I have always have decent gameshape when my players play between 48-70 minutes. Some people ideally say it is around 60 I think, but during the season I have most players at respectable or strong game shape...