Hey Sharky
The best way to do dips using the TRX is by taking a thumb grip on the handles and resting your heels on the ground. The TRX should be behind your arms and your back. This should allow you to do dips without the strap rubbing against you. To increase the difficulty you can elevate your feet.
There is another way that you will be able to configure the TRX so that it works similarly to the way rings work with a dual anchor. This serves to separate the straps and make movements like ring dips and muscle ups possible using the TRX while still allowing you to quickly change the configuration back to a single point to do all of the other exercises that are best done in the classic single point anchoring set up.
Keep your eyes on the blog as we should be posting something that includes video support on this in the upcoming weeks.
I hope that this helps in the mean time.