Trievel, over here in Europe $35 per month will not buy you a connection capable of being used reliably for this purpose. In fact, you'll rarely be hosting races at all if you do not invest quite a bit more than that.
I'll readily admit I know next to nothing about Call of Duty or other online shooters, Dragonistic. However, it would seem to me that for people willing to cheat in GT5P the TeamGT "private room" solution is not very beneficial.
If you want to use this method to make sure you get more wins in online racing, you'll have to use it to exclude the better drivers, because excluding drivers is all it can do for you. It will be very hard, without their cooperation in fact next to impossible, to identify those drivers by their IP addresses. So, all you can do is exclude the whole bunch, leaving you with a grid of one, and a sure win.
But even the saddest cheater of them all will not derive much satisfaction from pulling off a win in a race with only one car starting!