The more you load it up, the bigger the gearing will feel, the 53/39 will feel more like Pantani's 55/44 after you load it up.
IMHO, I would suggest switching to a compact (50/34), if 50t still a little too big, drop down to your suggested 48t or 46t wouldn't cost much, it will be useful to have a 34t when the time come.
You got 53/39?? that's a pretty huge gearing.
The more you load it up, the bigger the gearing will feel, the 53/39 will feel more like Pantani's 55/44 after you load it up.
IMHO, I would suggest switching to a compact (50/34), if 50t still a little too big, drop down to your suggested 48t or 46t wouldn't cost much, it will be useful to have a 34t when the time come.