"I always felt like it's probably a bad practice to do so."
It's not if it does the job. I get to say it again; You don't need code to run as fast as possible -- you only need fast enough.
Build it using the BIGGEST tools you can find -- the less work you have to do the sooner you can get a project done, profile it, then replace only the sections that mean you're not hitting your target.
Your goal is a completed project, not a tiny section of very-very-very-very spiffy code.