Captain America did this kind of thing all the time.
I had three math instructors at MATC before I went to UW. They were all practical math people (i.e. people with STE degrees). Of the 4 math professors I had at UW, only one was worth a damn. Both calculus professors and the DiffyQs professor couldn't be bothered with anyone who wasn't a math major. My linear algebra instructor was a visiting prof from Switzerland, and once I got used to his accent (French, btw), he was aces (and I mean that, he was happy to spend lots of time in office hours making sure you had it down).
Calc 2 & 3 were both ugly (I failed calc 2 the first time through, even though I got an A in Calc 1), and DiffyQs would have been, but by that time I had so much exposure to PDEs & ODEs in my engineering classes that it was almost old hat.