I have made 7ft 3pc single hand rods from 9ft 4pc SH rods and I like to use one wt-class lighter line.
I think you should use shorter head length and perhaps one wt class lighter as well.
If you build a shooting head and test cast a line which is too long when it "feels good" note that the section of line which you keep inside rod loads rod as well so you need to cut first two feet longer what you have out of rod tip. Then tie it to cheap mono line just stripping away 1/2'' of coating and then fold back the core and tie Allbright knot over line and naked core. Then test cast again. Perhaps you need to shorten head more but this way it is easier than adding weight.