Unfortunately I haven't play with any 16x19 (full weight) Rad.
But I've played a lot with IG Rad MP (18x20) and IG Prestige S.
Very different racquets.
Two things I remember the most:
- IG Rad MP is too underpowered (you have to string it very low) and besides its low stiffness vibrates as a hell...
- IG Prestige S has no control at all. And when you string it high (near 60's) in order to gain more control loses any feel it has (and it doesn't has any from the start).
So, my advice is to strung your Rad 18x20 MP as low as you can with a spin friendly wire...
PS: Head Graphene Radical S is a much better racquet from those two (more stable, nice feel, spin friendly), if you like a light 16x19 Rad and an easy platform racquet (you could make it much heavier).