My surgeon has suggested 610cc smooth HP under the muscle. I'm concerned that being smooth they might bottom out?

 The biggest risk factor for your implants bottoming out is the size and weight of the implant. A 610 mL implant is a very large implant and as such is very heavy. The tendency for an implant to bottom out is not dependent on the surface of the implant, but rather the weight of the implant and the ability of your tissues to hold it in place.  I would share your concerns with your plastic surgeon prior to surgery to better define this risk.  Good luck!

 600 cc implants sounds rather large for your small height and weight. Large implants are going to have more of a stretching and gravitational effect over time than smaller implants.Shaped,  anatomic implants, which are textured and have more cohesive gel will, in theory, adhere to the walls of the pocket and put less pressure on the bottom of the pocket. This will theoretically lead to less bottoming out over time.