5 1/2 weeks post op saline 600cc mentor implants under muscle, concern that they are riding too high. Does this look normal?

Congratulations on your recent surgery.  600 cc implants are large and will take some time for your body tissues to relax and allow them to settle lower.  Massaging continuously and going braless are all helpful in assisting your body muscles to stretch and implants to descend.  Keep following your plastic surgeons recommendations. 

Thanks for the question and the photos. The implants are in a high position. When I place implants in a sub muscular position, I keep them too high in anticipation that they will drop over the first few months. Be patient. You are only 5 weeks out. They will be in a better position within the next few months. 

You could wait some more time but I doubt they will come down to where you weant them.The implants to me are too big.

The transaxillary approach can have a somewhat increased risk of implants riding up and out, so it may take more time for settling. Massage may not help; usually it is a matter of time for the muscle and skin to relax and the implants to reach the bottom of the pocket. If they do not drop to where you both are happy at the 6 month mark, revision may be indicated, in which case you might need to consider an inframammary incision to release the lower pocket area.

Your implants are high and will drop some. The best is to wait at least 2 more months. The main concern is that your implants are too big for your breast and may have to change to smaller implants if not improved in few months

It is far too early to be concerned. You very large implants and it takes longer for the implants to stretch the tissues and drop. Wait at least 6 months before even thinking about the need for revision.