Safely running raceway overhead has many challenges. Fatigue of the shoulders and upper back from lifting and holding it overhead is a common problem.
Strategic rest breaks help prevent excessive buildup of lactic acid. But a better solution is to fabricate a set of raceway braces at the right height for that particular run. Rather than rig up something rickety, hire a carpenter to build a light-weight, stable, adjustable reusable one that can be bolted together onsite.