I think the parlay is a reasonable-looking play, so I don't think it would be a problem.
If you're playing at a place that you think would give you grief over a 1 to 5 spread instead of 1 to 4, maybe the extra bet isn't worth it. But I bet you're not concerned about a specific casino, and instead are trying to generally stay at 1 to 4. In that case, I don't think an occasional 5-unit bet would raise any red flags.
(I moved this thread from another forum, since the original post used the word 'spread'. I assume he's counting.)