The answer is...
1.) If you don't have any previous experience using it in the planned muscle group successfully, then you shouldn't use it at all. Otherwise, you risk water retention and possible temporary muscle deformation.
2.) If you have used it successfully in the past in the planned muscle group (which means it did not damage your muscle shape or cause noticeable sub-q water retention), then go for it. But...do NOT do anything you haven't done before. That means not injecting in a different muscle group or using a different dosage, injection frequency, injection dept, or injection placement. You want to know EXACTLY how you are going to respond before you start using SEO's the last minute of contest prep.