I believe your rod is built on the same blank as the Superfine "tippet" with a flex rating of (as you say) 4.5.
I have a Superfine 7/11 4 wt with the same flex rating. It is a soft, delicate somewhat graceful rod to cast. My rod anyway is a true 4 wt, no need to overline.
BTW..you can't make a 3 wt rod be a 4 wt by overlining it. You will find the rod useful just the way it is.