Yes, if you slam to hard on the slide hammer it will cause that dreaded outward dent. They are easy to spot since when you sand on it all you will see is bare metal where the stud was.
The studs and slide hammer technique is good for getting it close, you want like 1/8th inch of bondo in the low spot. Anything much more than that will most likely crack within a couple years of completing your paint job.
Anyone who has ever used the slide hammer has one thing on their minds they want to add so I thought I would add. Eventually you will nail yourself in the balls with the slide hammer, the studs can rip out of the panel and propel the hammer blow force in the direction you are sliding the weight. For some reason its always seems to be a straight shot to the balls, and then you learn to keep it pointed away from you.