[Henry Anthony]

Paul,

The reason it is a good idea is because once you have an existing stock component, like a motor - and hopefully an accurate model - you do not need to analyze the component to create a new sketch for a mounting plate. You just project the geometry and let Inventor do the work. It is a much more productive and intuitive method in my opinion. And you won't get that "Can't create a constraint..." thing anymore. Believe me, I have been there. It drove me crazy. If you need more help, just yell!