How soon after a TT can you start a diet to get rid of the last 5-10 lbs?

I think if you maintain a good and healthy eating lifestyle after you TT and start exercising on a regular basis when it's recommended by your PS, you should be able to see changes-don't be too hard on yourself though.  You are still healing

You should follow your surgeon's instructions regarding post-surgery care. It is important to do this so that your recovery is not compromised. You should be eating a healthy well-balanced diet and resume exercising after about 3-4 weeks, with strength training and core exercises after about 6 weeks.

If you haven't had your surgery yet, I highly recommend that you get to your goal weight prior surgery to get the best result. If you have had surgery, you should wait until 4 to 6 weeks before trying to diet. Your body needs good nutrition for healing. Be sure to eat a healthy diet and gradually cut back on calories. At 6 weeks you can start exercising, that and a proper diet is your best bet.

It's best to lose the weight prior to surgery to ensure more predictable and lasting results.  Good nutrition is important for the healing process following surgery, but some calorie restriction is Ok as long as you maintain a balanced diet.  It's best to consult a nutritionist to ensure the approprate regimen to obtain your weight loss goals without compromising your healing.

You should be eating a healthy diet after your surgery, including plenty of fruits and vegetables and restrict empty calories. That being said, you should not restrict your caloric intake by more than a maintance amount for the first month after surgery to assure wound healing.  After approx 4 weeks, you can begin restricting calories for weight loss.  Good luck!