Weak a/c--are these pressures OK?

[itb76]

I have searched and read numerous posts, and I'm still confused.

Tested my a/c today, and got the following readings:

'98 ML320
static pressure: 110
ambient temp: 80 (rose to over 90 during test)
RH: 65%
idle: 45 lo, 220-240 high
2000 rpm: 30/170

after the pusher fans kicked in and stayed on constantly: 40/200 at idle

center vent temp, fan on high, recirc off: 62
vent temp, cruising 40-60 mph: 55
vent temp, accelerating: 52

Usually takes a long time to cool this vehicle off; do these pressures indicate an undercharged condition? In another post I found that the ML320 holds less refrigerant than my Golf; I wonder if that's why the Golf's a/c works better.