Is a canthopexy without infraorbital rim implant, sufficient and reliable? (photo)

Canthopexy will NOT achieve what you want. If you want more almond shape eyes, few extra steps are required (see following video and link). Additional infraorbital rim implant can be placed during the procedure but it is not mandatory. 

A lateral canthopexy or even a canthoplasty alone is rarely adequate to lift the lower eyelid the whole way across to make for a more narrow eye shape. Infraorbital rim implants have value to helping correct under eye hollows and tear troughs and would be of benefit in conjunction with a canthopexy/canthoplasty should this skeletal deficiency.