As I said in another thread, and seems to be the general consensus - It would be easier to stretch something slimmer than something thicker.
So with that in mind yes it would be best to get to your length goals before you work heavily on girth. Some don’t work on girth at all, some just lightly.
It’s been reported in other threads that people have been gaining a little girth - usually at the base - from hanging. Something to consider.
Your goal is very ambitious in that time-frame, actually it’s impossible IMO. Some people won’t gain that much in a lifetime. You want it in 4 months?!
I’d advise you set up markers. Obviously you don’t want to get to 10” long with a girth of 4.7” (Though that WOULD be something to see. Lol)
What I mean is. In 4 months time, have a goal to be at 7.5” BP, and work from there, adjusting your goal every time. Perhaps working on girth after each length marker to move up accordingly.
Sure you can have an eventual goal of 10x7. But aiming so high without a clear cut plan will result in a lot of frustration IMO.
Good luck!