Well, to settle the question of whether the Pros are different from the others,
maybe paoloraz can post the data of his 300i Pro and jimbo for his 400i Pro and we can compare. I have the 400i and will be happy to measure it.
The problem is that, within the same weight category (say, L = Light) both the 200g and the 300i have a range of variability in terms of weight (it was officially printed in the cardboard inside the head when new)...
I weighted my 300i's weighted L (I also have a couple of LM).
They all have the original leather grip, are strung (but with different strings), no overgrip, no vibration dumpener. Here are the results:
300i L4 "grafil injection": gr. 360
300i L4 "graphite injection": gr. 366
300i L4 "graphite injection": gr. 372
300i L4 "graphite injection": gr. 373
300i L4 "graphite injection": gr. 351
300i PRO L2 "graphite injection": gr. 351
In the end:
1) The PRO is in the lower part of the weight distribution, but this does not imply that PRO's weight on average less...I have a regular one with the same weight and even with a bigger gripsize (in general, an L2 tends to weight less than an L4).
2) the lower extreme in the range of the Light wieight distribution is 350, then we jump up to 360-364 and, with another jump, to the upper extreme of 372
3) I also have many 200gs and the weight distribution (original gripsize, strung, no overgrips, etc) of racquets labelled Light is very similar and concentrated around the mass points 351-365-372
4) Not sure what it implies, but, similarly to the 300i PRO, my 200g PRO "graphite injection" is in the lower range (it weght 351) of the light weight distribution.