mismatching flyline weight with reel

hello everybody. i have a question here about reels and flylines. it's kind
of going against the grain so i was hoping some of you might chime in with
thoughts or personal experiences.

i have a redington CT 5/6 reel as well as an okuma integrity 5/6 large
arobor reel. these two reels are incredibly different in size and weight,
and i know the large arbor feature has a lot to do with it. at the moment
i'm using the okuma, keeping the redington in its case for future use in
some way.

i'm currently using a 9 foot 5 weight graphite rod. i'm exploring several
late season trout streams in my area and finding them very small but fun
still the same (most would be considered rivers at other times of the year).
if, ONE DAY, i purchase a second, smaller rod, could i use the smallish 5/6
redington on a 4 or 3 weight rod with 4 or 3 weight line? i guess what i'm
asking is would this cause any serious problems in performance?

thanks.