Would a sliding genioplasty be sufficient? I've ruled out a chin implant and don't want bimax surgery. (Photo)

From the looks of your profile pictures, a sliding genioplasty would improve your facial balance without needing a chin implant.  While a formal orthognathic surgery would likely be the best overall procedure for you, you could get a much stronger chin with a genioplasty alone.Find a board-certified surgeon in your area who has experience with all aspects of bony facial surgery - nothing can take the place of an in-person consultation.

You should do well with a sliding genioplasty. The key is to carefully evaluate all dimensions of the chin movement beyond just the horizontal one seen in profile view. The height of the chin and its width in the frontal view are also equally important since this is how you see yourself more often. All of these dimensions can be changed with the bony movements provided by a genioplasty movement. 

Given your parameters, a genioplasty would be fine. But the advancement has to consider the narrowness of your face/jaw; so that the overall look does not get compromised when viewing from the front as opposed to profile. Tapered narrow jaws often need augmentation of the area behind the chin as well in a limited fashion in order to ensure a natural even jawline