I'm sure you can find up to 120cm poles on Osculati website, both in s/steel and teak, but 5 feet....
I suspect you need a custom job at that size.
You must have quite some boat, to require a pole that long!
Short answer, yes.
Also because when a flag doesn't take at the very least two thirds of the pole height, it looks out of place.
As it does in your pic, very frankly speaking.
In your boots, I think I would either
1) not care if the tender covers the flag, or
2) consider a smaller pole/flag above the arch.
But that's me, of course. Each to their own!